The Kremlin on Thursday warned against speculating what may have caused an Azerbaijan Airlines flight to crash, killing 38 of the 67 on board, after an aviation expert said evidence indicated that a Russian anti-missile battery may have brought down the passenger plane.

An Azerbaijan Airlines flight that crashed in Kazakhstan on Wednesday killing 38 people was downed by a Russian air defence system, four sources in Azerbaijan with knowledge of the investigation told Reuters.

Officials in Azerbaijan believe a Russian air defence missile caused the crash of a jet on Christmas Day which killed 38 people, according to multiple media sources.