No air defence missile systems have ever been sent from Russia to Ukraine, Moscow military officials insist - contrary to the findings of the Dutch-led investigation into the 2014 downing of Malaysia Airlines flight MH17.

Defence Ministry spokesman Major General Igor Konashenkov argued that the investigators' conclusions raise doubts, claiming they were based on information from the internet and Ukrainian special services.

The flight was downed on July 17, 2014, by a missile over eastern Ukraine - killing all 298 people on board.

Dutch-led investigators said it was downed by a Buk missile from an area controlled by Russia-backed separatists.

They said the launcher had been brought in from Russia and was later returned back to Russia.

Maj Gen Konashenkov denied that, saying "Russian missile defence systems, including Buk, have never crossed the Russian-Ukrainian border".

The Russian maker of the Buk missile system also contested the conclusions of the investigation.

Mikhail Malyshevsky, an adviser to the director of the state-controlled Almaz-Antei consortium, said an analysis of the plane's shrapnel-ridden fragments show that it could not have been downed by a missile launched from a rebel-controlled area in eastern Ukraine.

He said the missile likely came from an area that Russian officials have previously described as Ukraine-controlled.