Update: 6:45 p.m.
Britain's newly minted foreign secretary, Philip Hammond, called for a "U.N.-led investigation into the facts" of the crash of Malaysia Airlines Flight 17, saying he was "deeply shocked" by the incident, and noting that an unknown number of British nationals were on board the plane.
"As yet, we do not have any definitive information about how this incident occurred, and I don't want to speculate at this stage," he said in a statement issued by the British Foreign Office.
"This must be resolved by an international investigation," he said, adding that British authorities were still trying to determine the number of British nationals on board the plane when it crashed in Ukraine.
"We believe the United Nations, particularly the United Nations civil aviation organization, is the right body to lead that investigation," Hammond said. "We are prepared to make Air Accident Investigation Branch assets and specialists available to aid such an investigation."
Update: 6:35 p.m.
In a televised statement, Russian President Vladimir Putin said that Ukraine bore sole responsibility for the crash of Malaysia Airlines Flight 17, a "disaster" that he said would not have occurred if Kiev had not resumed its military campaign against pro-Russian separatists.
"And without doubt the government of the territory on which it happened bears responsibility for this frightening tragedy," he said, before adding that he had urged Russian authorities to do everything possible to help investigate the incident.
Meanwhile, the prime minister of the breakaway Donetsk People's Republic, Aleksandr Borodai, also weighed in on flight MH17. Borodai said the wreckage had landed near the town of Torez in eastern Ukraine and added that the Donetsk People's Republic does not possess weapons capable of shooting down a passenger plane. Beyond denying the attack, Borodai also said that the Donetsk People's Republic is committed to an impartial investigation and is willing to permit foreign investigators to inspect the crash site.
Earlier on Thursday, the first deputy prime minister of the Donetsk People's Republic announced that MH17's black boxes will be given to Russian officials for investigation.
The White House also announced that President Obama spoke with Ukrainian President Petro Poroshenko on Thursday afternoon. According to a White House statement, the two men "emphasized that all evidence from the crash site must remain in place on the territory of Ukraine until international investigators are able to examine all aspects of the tragedy."
Update: 6:15 p.m.
Malaysia Airlines has identified the nationalities of a majority of the 298 people aboard Flight 17. (Earlier reports of the number of passengers and crew had put the figure at 295.) Though a comprehensive list is still to be released, among those on board were 154 Dutch citizens, 27 Australians, 23 Malaysians, 11 Indonesians, six Brits, four Germans, four Belgians, three Filipinos, and one Canadian. French officials have said there were at least four of their citizens on board the flight, but that figure has not been confirmed. Some reports have indicated there were 23 Americans on board, but the U.S. State Department has not confirmed the figure.
Update: 5:35 p.m.
U.N. Secretary-General Ban Ki-moon called for an independent probe into the crash of Malaysia Airlines Flight 17 in Ukraine.
"There is clearly a need for a full and transparent international investigation," he told reporters at a U.N. press conference he had convened to introduce his new special envoy to Syria, Staffan de Mistura. "I am closely monitoring the reports, along with the International Civil Aviation Organization, a United Nations agency."
"For the moment, I offer my deep condolences to families and loved ones of the victims and people of Malaysia," Ban added.
Update: 4:55 p.m.
Malaysian Prime Minister Najib Razak said that he had spoken by phone to President Barack Obama, and that both leaders agreed only crash site investigators should have access to Malaysia Airlines Flight 17's black boxes, which could contain essential clues for determining how the plane was brought down. Earlier, pro-Russian separatists had announced their intention to hand over the jet's cockpit voice recorder and its flight data recorder to Moscow for analysis.
Razak also said that he'd spoken with Ukrainian President Petro Poroshenko, who said he would work with rebels in the eastern portion of the country to establish a "humanitarian corridor," so that investigators could reach the crash site. Razak said the Malaysian government has dispatched a flight to Kiev carrying investigators, who will arrive at the scene and "leave no stone unturned" in their efforts.
Separately, U.S. intelligence officials now say that the airliner was brought down by a surface-to-air missile, although it remains unclear who fired it. In remarks at an event in Detroit, Vice President Joe Biden said that it appeared that the plane had been deliberately shot down.
Update: 4:35 p.m.
The Kyiv Post reports that Ukraine's main security agency, the SBU, has released recordings of intercepted phone calls between separatists and Russian military intelligence officers, in which the militants admit to shooting down the civilian plane.
"It's 100 percent a passenger (civilian) aircraft," a militant identified as "Major" says, noting that there are no weapons on the site. "Absolutely nothing. Civilian items, medicinal stuff, towels, toilet paper." He describes the group who shot down the plane as "Cossacks."
The SBU also released a call between Igor Bezler, a separatist leader of the Donetsk People's Republic and an alleged Russian military intelligence officer, and Vasili Geranin, identified as an intelligence colonel in the headquarters of the Russian army. "We have just shot down a plane," Bezler says.
The militants on the call appear surprised that they had shot down a civilian plane. The militant identified as "Greek" inquires into what type of plane was shot down and about the passengers onboard. The other militant, "Major," says that, "It's totally f****d. The pieces are falling right into yards." Upon finding out that the flight was "100 percent" a civilian aircraft, "Greek" continues to ask questions until it is revealed that one of the passengers was an Indonesian student. If these rebels are indeed responsible for shooting down the airliner, it does not appear that they were aware that they were targeting a civilian aircraft when they fired.
The recordings of the calls, in Russian, can be heard in the video below.
Update: 4:00 p.m.
With confusion and conflicting reports on the crash of Malaysia Airlines Flight MH17, some essential facts will only be known once investigators reach the wreckage. However, it appears that Ukrainian officials and rebels are competing for control of the crash site, with the Donetsk People's Republic claiming possession of the Boeing jet's black boxes, which would have recorded the pilots' last words and may provide vital clues about what brought down the jet. The rebels have announced that they intend to deliver the boxes to Moscow.
First Deputy Prime Minister Andrei Purgin of the Donetsk People's Republic promised that the black boxes will be transferred to Moscow for examination, saying that Russian officials are "highly qualified experts who will be able to accurately determine the cause of the disaster, even though it is so clear."
Commercial airlines are required to have two black box recorders on board flights, with one black box recording audio from the cockpit and another cataloguing flight information such as altitude, speed, and fuel during the flight. Having access to such information will be significant for determining what happened to the Malaysian airliner. Vladimir Puchkov, a spokesman for the Russian agency responsible for investigating plane crashes, told Russia's RIA Novosti news agency that Russian emergency services sent an official request to their Ukrainian counterparts for a joint investigation on Ukrainian territory. So far, Ukrainian officials have not responded to Russia's call for cooperation, although Ukrainian President Petro Poroshenko announced the formation of an investigative committee into who and what is responsible for MH17's destruction.
Update: 3:40 p.m.
A spokesman for the Russian Embassy in Washington declined to comment on charges that pro-Russian rebels in Ukraine shot down a Malaysia Airlines plane. "Why should we comment on allegations?" the official said. The spokesman did, however, point to an article published by the Russian news service RIA Novosti suggesting that the Ukrainian military shot down the aircraft, not the rebels.
The article, which cited "reconnaissance data" supplied by an anonymous source, notes that a Ukrainian army battalion with Buk air defense systems was deployed near Donetsk on Wednesday morning, "making the downing of the aircraft by one of the missiles highly probable," the article says. The anti-aircraft system is capable of shooting down planes flying at the altitude of commercial airliners.
The source in the article also raises doubts that pro-Russian rebels could have carried out the attack, claiming that the armed militia in eastern Ukraine "does not have Buk systems." Both the Ukrainians and pro-Russian rebels deny shooting down the passenger plane.
In a sign of the crisis' growing international dimensions, Britain privately called for an emergency session of the U.N. Security Council, according to a council diplomat. The diplomat said that the session would likely take place tomorrow afternoon, but that the council's 15 members were still discussing the timing of a council meeting.
-John Hudson & Colum Lynch
Update: 3:25 p.m.
How and by whom was Malaysia Airlines Flight 17 shot down -- if it was shot down? That's the central question being debated in the aftermath of the plane's crash. And the discussion is centering on a medium-range Russian anti-aircraft system known as the Buk, which a Ukrainian Interior Ministry official claims was used to down the aircraft.
As we reported earlier in the day, pro-Russian separatists in eastern Ukraine claim that they lack the capability to shoot down a plane traveling at the altitude of a commercial airliner. Reports indicate that the Malaysian Airlines flight was traveling at 33,000 feet when air traffic controllers lost contact with it. Man-portable air-defense systems -- known as MANPADs -- that are in the separatists' possession lack the range to reach that altitude. But defense experts say that the Buk would have no trouble downing a plane at more than 30,000 feet.
Following the plane's crash, the rebels denied having access to the Buk, but in recent weeks, there have been widespread reports of separatists acquiring the weapon, and possibly other surface-to-air missiles, as well. On June 29, the Russian newswire ITAR-TASS reported that rebels in the self-proclaimed Donetsk People's Republic had acquired Buk missiles. The group even tweeted about having acquired the weapons.
And while it remains unclear who may have been responsible for shooting down the plane, Buk missiles -- or weapons similar to them -- were spotted in separatist-held territory near where the plane went down. An Associated Press reporter spotted what was described as "a launcher similar to the Buk missile system" near the town of Snizhne.
On Thursday, a Twitter account associated with the Maidan protest movement in Kiev posted a photograph purporting to show a Buk launcher in the town of Torez, which is near the crash site and has been the scene of fighting between separatists and government forces.
Crucially, the Ukrainian armed forces also have the Buk missile system, which gives Russia and its proxies a measure of plausible deniability if it is confirmed that a Buk was indeed responsible for downing the Malaysian jet. According to Patrick Megahan, a research associate for military affairs at the Foundation for Defense of Democracies, the Ukrainian military has been operating Buks in the area near the crash site, raising the possibility that Ukrainian forces made a mistake.
Still, the only known uses of Buk missiles in eastern Ukraine have been directed at government targets. "The Buk is the same system that reportedly took down a twin-engine Ukrainian military cargo plane on Monday -- an attack believed to be carried out by Russian separatists," Megahan told Foreign Policy. "It is likely the only system in their arsenal that could take down an aircraft flying at that altitude."
The missile system, designed in the Soviet era and produced in Russia, was heavily used during the Russian invasion of Georgia in 2008. "It's a very capable system, proven under real-world conditions," Andrew Bowen, a columnist for the Interpreter and a researcher at the political risk consultancy Wikistrat, told Foreign Policy. It's also not an easy weapon to fire, and would require some training or prior knowledge to use it. "These systems require a large amount of technical know-how, unlike these MANPADs, which are basically 'point-and-shoot,'" Bowen said.
-Elias Groll, Reid Standish, Hanna Kozlowska, and Kate Brannen
Update: 1:55 p.m.
After the reported shoot-down of a Malaysian passenger jet, major airlines say they are avoiding the area in which the plane went down. Lufthansa, Air France, Turkish Airlines, and Russian airline Aeroflot all said they will be diverting their planes from Ukrainian airspace. "Air France is monitoring the situation in real time and decided to no longer fly over eastern Ukraine after it was informed of this incident," a spokesman for Air France said, according to Reuters.
Update: 1:10 p.m.
Prior to the Malaysian Airlines jet's being shot down, pro-Russian separatist leader Igor Strelkov posted on the Russian social networking site VKontakte, claiming responsibility for shooting down a Ukrainian AN-26 transport plane. However, after news emerged of the downed Malaysian Airlines plane, Strelkov's page appears to have been scrubbed of the post.
Strelkov's page claimed responsibility for taking down a Ukrainian jet and posted an accompanying video that shows smoke rising from what is now believed to be the crash site of the passenger jet. Below is a screen grab of Strelkov's VKontakte page that includes the post claiming responsibility for the downed transport plane. That post now appears to have been removed.
Donetsk separatist boss Strelkov, Kremlin's proxy in war, says he ordered shootdown thinking plane was Ukrainian pic.twitter.com/uaWKVlsA7q— Strobe Talbott (@strobetalbott) July 17, 2014
After reports emerged that a passenger jet had been shot down, Strelkov said that his forces were not responsible and that they lacked the capability to shoot down a plane flying at that altitude. The plane was reportedly flying at an altitude of about 33,000 feet.
Meanwhile, additional images are emerging of the crash site, including the horrifying image below, which was carried by Russian television:
Russian television showing absolutely horrifying pictures of the crash site. pic.twitter.com/Nf18BZf2q0— Chico Harlan (@chicoharlan) July 17, 2014
-Elias Groll & Reid Standish
Update: 12:45 p.m.
Reports are emerging from eastern Ukraine that Russian forces may have shot down a Malaysia Airlines jet near the Ukrainian-Russian border. Malaysia Airlines has confirmed that they have lost contact with the jet, a Boeing 777 that was traveling from Amsterdam to Kuala Lumpur with 295 people on board.
According to a report carried by the Interfax news service, citing unnamed sources in the aviation industry, the plane was shot down.
Writing on his Facebook page, Anton Gerashenko, an adviser to the Ukrainian interior minister, blamed Russian forces for downing the jet, saying that "there is no limit of cynicism for Putin and his terrorists." He offered no direct evidence that Moscow was responsible. Gerashenko added that the plane was shot down by a Buk launcher. The Associated Press reports that rebels in Ukraine have such a system.
Public flight trackers show the flight disappearing just outside Donetsk, near the Ukrainian border with Russia, which has been the scene of intense fighting in recent weeks between Ukrainian armed forces and pro-Russian separatists.
U.S. officials said they were tracking reports of the crash but had no indications whether it was or wasn't shot down. A White House spokesperson said that President Barack Obama "is aware" of the crash. Officials continue to monitor events.
Separatists in eastern Ukraine denied responsibility for shooting down the jet, saying they lacked the equipment to shoot down an airliner at the altitude a commercial passenger jet flies. Ukrainian President Petro Poroshenko said that Ukrainian forces in the area did not fire any anti-aircraft missiles in the area.
Videos circulating on social media purport to show flames rising from the crash site outside Donetsk. In the video below, villagers celebrate as smoke rises on the horizon. "It burns beautifully," one man says, in all likelihood believing that it is a Ukrainian military plane that has been shot down.
Unconfirmed photographs circulating on Twitter show debris scattered near Donetsk that appear to comes from a Malaysian Airlines jet:
Reports of the airliner's downing come on the heels of news this week that Russian forces allegedly downed a pair of Ukrainian military planes. On Thursday, the Ukrainian Security Council said that a fighter jet had been shot down by a Russian air-to-air missile. On Monday, Ukraine said a transport plane was downed by a Russian missile. In addition to reports of Russian forces firing on Ukrainian planes, reports have emerged this week showing Russian forces launching rocket strikes on Ukraine across their shared border.
-Elias Groll & Reid Standish
DOMINIQUE FAGET/AFP/Getty Images