President Vladimir Putin on Saturday apologised to Azerbaijan's leader for what the Kremlin called a "tragic incident" over Russia in which an Azerbaijan Airlines plane crashed after Russian air defences were fired against Ukrainian drones.

Russian President Vladimir Putin apologized for the plane crash in Russian air space on Christmas Day that left 38 people dead in a statement that said Russia was targeting Ukrainian drones over the plane’s planned destination at the time, but stopped short of taking responsibility.

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