It happened on Shell Expro's North Cormorant installation just before 1400.

A statement from the company said safety systems operated as designed and shut down production.

There were 91 people on the platform at the time. Shell said they had all been accounted for and there were no reports of any injuries.

A Coastguard helicopter and two civilian aircraft were used to airlift non-essential personnel from the platform, which is about 109 miles north-east of Sullom Voe in Shetland.

The company has informed the Health and Safety Commission, according to statutory regulations.

There are details about the cause of the gas leak.

The North Cormorant started production in February 1982.