Malaysia Airlines flight MH17 was hit and downed by a Russian-made surface-to-air BUK missile over eastern Ukraine last year, the Dutch Safety Board said.

"Flight MH17 crashed as a result of the detonation of a warhead outside the airplane against the left-hand side of the cockpit," the chairman of the Dutch Safety Board, Tjibbe Joustra, told a press conference on Tuesday.

"This warhead fits the kind of missile that is installed in the BUK surface-to-air missile system."

While he insisted investigators had not pinned down the exact location of the missile's launch site, maps shown to reporters clearly showed the area near Donetsk held by pro-Russian separatists.

Even before the highly-anticipated release of the official report on the disaster, Russian officials were disputing the findings which are sure to further degrade strained ties between Moscow and the West.

Joustra also hit out at the Ukrainian authorities for allowing civil aircraft to continue to fly above the eastern part of the country despite the raging conflict between Kiev's forces and pro-Russian separatist insurgents.

Visibly shaken

"We have concluded as a precaution there was sufficient reason for the Ukrainian authorities to close the air space above the eastern part of their country," he said.

Relatives earlier emerged visibly shaken after being privately briefed by Joustra in an conference centre in The Hague about the fate of the Boeing 777 which was en route from Amsterdam to Kuala Lumpur when it went down on July 17 last year.

Relative Robby Oehlers said a wave of sadness had swept through the room.

"They showed us the fragments that were inside the plane," Oehlers said, adding in the room "it was so quiet, you could have heard a pin drop."

Findings disputed

The findings were swiftly disputed by the missile maker Almaz-Antey, which has carried out its own tests into the crash.

The Russian company had performed a test which "disputes the version of the Dutch," and the damage to the MH17 pointed to the use of an older type of missile.

"The results of the experiment completely dispute the conclusions of the Dutch commission about the type of the rocket and the launch site," said Yan Novikov, director of Almaz-Antey.

Ukrainian Prime Minister Arseniy Yatsenyuk meanwhile blamed Russia's security service.

"I personally have no doubt that this was a planned operation of the Russian special services aimed at downing a civilian aircraft," Yatsenyuk told a televised cabinet meeting.

The long-awaited findings of the board, which was not empowered to address questions of responsibility, did not specify on Tuesday who launched the missile.

All 298 people - most of them Dutch and including 80 children - died in the crash on July 17, 2014.

Source: Agencies