Thousands of shoppers and staff fled in terror when a fire reportedly caused by Christmas tree short circuit erupted inside a shopping mall today in Bangkok, Thailand.

The blaze started inside the Central World building in the heart of the Thai capital shortly after 4pm local time.

Footage shows how shoppers and staff began running out of the busy building as sprinklers were activated. Thick clouds of grey smoke were also seen inside the mall.

Dozens of police cars and fire crews were seen racing to the building to battle the inferno. People evacuated from the building gathered outside as alarms sounded.

The fire reportedly started when an electrical short circuit ignited a Christmas tree under an escalator on the seventh floor of the building near the cinema.

The number of injuries is not yet know.