A Greek-operated bulk carrier was hijacked off the Somali coast on Thursday and its crew of 25 taken hostage by pirates, a maritime watchdog said.
Noel Choong, head of the Kuala Lumpur-based International Maritime Bureau's (IMB) Piracy Reporting Centre, said the vessel was attacked about 200 nautical miles from the Somali capital Mogadishu.
"The pirates attacked and boarded the ship, she was en route to Kenya with a crew of 25 on board. It happened at 0250 GMT, it appears the pirates are now targeting ships on the eastern side of Somalia," he told AFP.
Choong said that since January, 55 ships have been attacked off Somalia and in the Gulf of Aden, and that 11 were currently being held for ransom.
Last year, the pirates had been operating on Somalia's east coast, but then shifted to the north, in the Gulf of Aden, before again recently switching back to the east, he said.
Somali waters are the most dangerous in the world for pirate attacks.
Maritime experts say many attacks go unreported along Somalia's 3,700 kilometres (2,300 miles) of coast, which is infested by pirates who operate high-powered speedboats and carry heavy machine guns and rocket launchers.
On Tuesday, French commandos freed a couple seized by pirates in the second such mission this year, leading President Nicolas Sarkozy to call for an international crackdown on sea raiders.