Four sources with knowledge of the preliminary findings of Azerbaijan's investigation told Reuters that Russian air defences mistakenly shot it down.

Russian President Vladimir Putin apologized to the President of Azerbaijan for the crash of the civilian airliner that killed 38 people, the Kremlin said Saturday.

The extremely rare publicised apology from Putin was the closest Moscow had come to accepting some blame for Wednesday's disaster, although the Kremlin statement did not say Russia had shot down the plane.