Azerbaijan on Thursday observed a nationwide day of mourning for the victims of the plane crash that killed 38 people and left all 29 survivors injured as speculation mounted about a possible cause of the disaster, with some experts saying that the airliner was damaged by Russian air defense fire.

Azerbaijan held a day of mourning on Thursday for the dozens of victims of an airliner crash in Kazakhstan, as questions were being asked over the cause of the disaster.

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.