The Centauri, a Maltese-flagged freighter with a crew of 25 Filipinos, was attacked some 200 miles south of Mogadishu, in the Indian Ocean, officials said.

"The pirates attacked and boarded the ship, she was en route to Kenya with a crew of 25 on board. It happened at 2.50 a.m., it appears the pirates are now targeting ships on the eastern side of Somalia," Noel Choong, head of the International Maritime Bureau's (IMB) Piracy Reporting center in Kuala Lumpur said.

Fifty-five ships have been attacked off Somalia and in the Gulf of Aden since January and 11 are still being held for ransom, Choong said.

This week French commandos freed a French couple who were seized on their yacht in the region and France's President Nicolas Sarkozy called for an international offensive against piracy.

Somalia's long and largely unpatrolled coastline is infested with pirates, making the Gulf of Aden and neighboring areas in the Indian Ocean among the most dangerous waters in the world.

In recent months, a Djibouti-based multinational taskforce has been patrolling parts of the Gulf of Aden and the Red Sea, where a pirate mothership is believed to be operating.

Andrew Mwangura, who runs the Kenyan chapter of the Seafarers Assistance program, said the latest attack was evidence that the pirates could play cat and mouse with foreign navies.

"They are changing locations due to the heavy concentration of navy ships" near the Gulf of Aden, he said.