THE British naval officer commanding the fleet of European warships sent to deter Somali pirates has warned that the pirates are becoming "better-armed and more professional".

Rear-Adm iral Philip Jones, who is in charge of the six warships attached to the European Union Naval Force for Counter-Piracy, said that while the force had had some success deterring "amateur" attacks in the Gulf of Aden, recent hijackings in the Indian Ocean off the coast of Somalia appeared to be the work of new, better-organised gangs which could range far out to sea in so-called mother ships.

"In the Gulf of Aden we saw a lot of opportunist attacks from people who are part-time fishermen," Rear-Admiral Jones said.

"The more recent attackers seem to be more sophisticated, with access to better arms and equipment." The foreign anti-piracy patrols were merely "scratching the surface" and the only real solution was for proper security on the lawless Somali mainland.

A spate of attacks in the past fortnight, which included the abduction of the captain of a US-flagged cargo ship, Maersk Alabama, comes after a lull of nearly three months. Rear-Admiral Jones said that was partly due to the recent monsoons.

He said the pirates were less easily deterred if a ship put up a fight and the prospect of earning millions of dollars from ransoms meant most pirates deemed the risks worth taking.

On Saturday, Dutch commandos freed 16 Yemeni fishermen taken hostage on their boat, and briefly detained nine suspected pirates who had forced their captives to use the boat as a "mother ship" during an unsuccessful attack on a Greek-owned ship, the Handytankers Magic.

A Dutch defence ministry spokesman, Robin Middel, said the commandos seized and destroyed seven AK-47 assault rifles and a rocket launcher. Mr Middel said the suspects had to be freed.

"There exists no legal framework in NATO for arrests to be carried out," he said.

Telegraph, London; Agence France-Presse