Chinese President Xi Jinping on Thursday sent condolences to the presidents of Azerbaijan, Russia and Kazakhstan for the casualties caused by the Azerbaijan Airlines plane crash, China's state broadcaster CCTV reported.

National flags were lowered across Azerbaijan, traffic across the country stopped at noon, and signals were sounded from ships and trains as the country observed a nationwide moment of silence.

Azerbaijan is observing a nationwide day of mourning for the victims of the air crash that killed 38 people and left all 29 survivors injured as speculation mounted about a possible cause of the crash

Officials in Russia and Kazakhstan are urging people to wait for an investigation into the deadly Azerbaijan Airlines plane crash before assigning blame.

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.