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.

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.

Russia and Kazakhstan have tried to calm speculation about the cause of the Azerbaijan Airlines plane crash, following claims it had been shot down by Russian air defence systems. On Thursday, Moscow urged calm as its foreign minister said it would be wrong to come to conclusions before an investigation into the crash was complete.