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.

An Azerbaijan Airlines flight that crashed in Kazakhstan on Christmas Day was downed by a Russian air defence system, a preliminary investigation has found, according to reports.

Taiwan's Presidential Office conducted its first ever tabletop exercise simulating a military escalation with China, several officials briefed on the matter said, at a time when the island is facing renewed Chinese military threats.