An offshore helicopter was forced to return to base in heavy fog after an alert over the North Sea.

The Super Puma aircraft landed safely at Aberdeen Airport with 20 people aboard shortly before 9.30am on Tuesday.

The crew were alerted to the problem by a cockpit warning light but operator Bristow said the reason for the alarm is unclear.

The helicopter’s pilot requested priority landing after turning back to Aberdeen because of heavy fog.

A spokeswoman for Bristow said: "One of our Airbus EC225 helicopters requested priority landing at Aberdeen Airport due to heavy fog while returning to base after a cockpit warning light.

"The helicopter landed safely at 9.28am with 18 passengers and two crew aboard. As usual, the aircraft will undergo a full engineering investigation to establish the cause of the warning light."