Russian state-owned producer of Buk missiles seeks to distance itself, as well as Moscow, from the downing of the MH17 flight which is widely assumed to have been caused by a Russian-made Buk missile.

Malaysia Airlines flight MH17 was brought down by a Buk ground-to-air missile, which exploded near the Boeing's cockpit then peppered the plane with shrapnel, a state-run Russian weapons manufacturer says.

The claim confounds previous Kremlin claims that the flight was shot down by a Ukrainian fighter jet.

Moscow-headquartered Almaz-Antey – which has manufactured Buk missile systems since 2002 – said it conducted its own analysis of the pattern of damage seen on pieces of MH17 wreckage recovered from the fields of eastern Ukraine.

REUTERS Yan Novikov, chief executive of Russian missile manufacturer Almaz-Antey, speaks about the crash.

That analysis showed that a Buk-M1 missile exploded 3-4 metres from the plane, close to the left side of the cockpit.

Fragments from the warhead then hit the left wing and the left engine.

There was a distinctive "double-T shape" to the damage which narrowed down the type of missile used, Mikhail Malisevskiy​, chief engineer at the company, said at a news conference in Moscow on Tuesday, according to reports.

"If the Boeing was downed with an air defence missile, it could be only Buk-M1 and this type of missile," the company's director Yan Novikov told reporters.

Malisevskiy said that type of missile was out of production in Russia but the Ukraine army had 991 such missiles at the time of the attack.

The company also claimed it could prove the missile was shot from a region controlled by Kiev's forces, not separatists. The Russian military has previously made similar claims.

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Almaz-Antey held the press conference to try to persuade the EU to lift sanctions against it, by showing it could not have manufactured the missile that brought down MH17.

All 298 people on board MH17 died in the crash on July 17 last year, including 27 Australian citizens.

Eliot Higgins, a British citizen journalist who has co-ordinated a 'crowd-sourced', international effort to investigate the MH17 crash, said the Almaz-Antey press conference marked a significant back-down by Russia.

"This is probably as close as we are going to get to Russia admitting that a Buk missile was used to shoot down MH17," he said.

Investigators work near a sign reading "No entrance! There may be remains of the victims of flight MH17 crash at the territory" at the site of the crash. Photo: REUTERS

The prevailing counter-narrative, promoted by Kremlin's so-called "troll army" of patriotic bloggers, had been that a Ukrainian SU-25 plane shot down MH17.

However the story was forced to change in the face of mounting evidence, including that gathered by Higgins' "Bellingcat" group.

Higgins said the company's theory as to the launch site of the missile did not match available evidence – and in any case still pointed to an area controlled by Russia-supported separatists.

"All the evidence points in one direction," he said. "If they want to stick with this (alternative) launch site they have to explain why it is in separatist territory, and why no-one saw it there."

His group had persuasive evidence, including satellite photographs, eyewitness reports and video, that the Buk missile launcher had arrived from Russia a few weeks before, was fired from separatist-controlled territory, and then returned to Russia, he said.