The British navy and an EU anti-piracy surveillance plane intercepted 10 Somali pirates and destroyed their two small boats off the Tanzanian coast, the British embassy saidto day.

The Somalis were spotted some 240 kilometres (150 miles) off the Tanzanian coast last Friday in a large vessel towing two smaller boats by the EU naval force aircraft and a chopper from the British warship HMS Chatham.

The frigate then dispatched a team towards the vessel.

"After monitoring the vessel through the night, at dawn, in a well planned operation, the pirates were forced to surrender by the overwhelming force posed by HMS Chatham, her Lynx helicopter and fast boats containing the ship's royal marines detachment," a statement said.

"The royal marines team boarded the larger craft and found 10 Somalis and a large amount of fuel on board," it said, adding that the suspected pirates had been seen throwing items into the sea, including their weapons and equipment.

The two small boats fitted with powerful outboard engines were detached from the larger vessel and destroyed.

"Disarmed and without the means to commit an act of piracy, the 10 Somalis were left with only enough fuel in the larger vessel to return to Somalia," the statement explained.

The HMS Chatham is part of the EU anti-piracy force patrolling the waters off Somalia, where ransom-hunting sea bandits have been hijacking a growing number of vessels.