Dramatic mobile phone footage has emerged showing debris falling from the sky and a black plume of smoke moments after flight MH17 was struck by a rocket.
The footage has garnered more than 100,000 views on YouTube after it appeared on a social media account purporting to belong to senior pro-Russian separatist Igor Strelkov.
Strelkov, known to his fighters as "Igor the Terrible", is the top military commander of the self-proclaimed Donetsk People's Republic.
He posted a link to the video on the Russian website VK less than an hour after flight MH17 was shot down.
Alongside the link, Strelkov appeared to take responsibility on behalf of the separatists for shooting down an aircraft.
The post, which was later deleted from the VK account, read: "We warned you, stay away from our skies."
However, the post claimed credit for shooting down an AN-26 military transport plane, not a commercial airliner.
"We just downed an AN-26 near Torez. It is down near the Progress mine," it added.
The confusion raises the possibility that pro-Russian separatists might have mistaken the Malaysia Airlines jet for a military aircraft, and shot it down in error.
In the video three men - who are reported to be pro-Russian rebels - are heard talking about debris falling from the sky.
"We just saw a plane being blown to pieces," one of the men says.
Another man describes the initial explosion he witnessed as "a blast" and praises the precision of those who shot the plane down.
"Wow, that was a blast," says the first man, who adds that he thinks the plane was "hit by a rocket".
Sky News has not been able to independently verify the authenticity of the footage, and it is not certain that the VK page is operated personally by Strelkov.
Strelkov is an elusive figure who is sought by Ukrainian intelligence officials as the top Russian operative in the separatist east.
He uses at least three aliases, and has vowed to "destroy" Ukrainian forces in Donetsk.
Kiev claims the separatist fighter is an agent of Russia's military intelligence.
Asked about Strelkov's background in May this year, separatist spokesperson Stella Khorosheva said he was an ethnic Russian and a veteran of the Soviet and Russian armies.
She gave no further details about his origins of his citizenship.
"His aides do not know if he has any other names. He has rich military experience and holds the rank of colonel," she said.
Meanwhile, the separatists have given crash investigators access to the site and journalists have been encouraged to take pictures, many of which are too graphic to show.
The names of nine British victims who were on board the plane are emerging. One was Glenn Thomas, a media officer at the World Health Organisation who was on his way to a summit in Australia on AIDS.
And one UK couple have been speaking of their shock after they were told they had to miss the flight because there were not enough seats.