Pirates have attacked and taken control of the Saudi-owned crude carrier Sirius Star off the east coast of Africa, a spokesman for the Bahrain-based US Navy Fifth Fleet says. Lieutenant Nate Christensen's confirmation on Monday followed a statement saying that the super tanker, which is owned by Saudi Aramco, came under attack more than 450 nautical miles southeast of Mombasa, Kenya. The 318,000-tonne vessel, launched earlier this year, is flagged in Liberia and operated by Vela International.

"This represents a fundamental change in the ability of the pirates to be able to attack large vessels off the coast," Christensen said. "This attack is obviously so different because of the size of the the vessel,  three times the size of a US aircraft carrier . I dont have specifics as to what is happening now. The vessel itself is going to remain under pirates' control."

The ship is carrying 25 crew members from Croatia, Britain, the Philippines, Poland and Saudi Arabia, the statement said. Christensen said the fate of the crew was unknown. He said the latest hijacking occurred despite a 25% drop in attacks by pirates since August. The International Maritime Bureau has reported that at least 83 ships have been attacked off Somalia since January, of which 33 were hijacked.

Of those, 12 vessels and more than 200 crew were still in the hands of pirates