Somali pirates attacked a large U.S. container ship with 21 American sailors on board - creating the first dynamic foreign policy crisis for President Barack Obama.
The 17,000-ton Maersk Alabama was one of a handful of U.S.-flagged and crewed vessels that are chartered by the Pentagon's Military Sealift Command to deliver supplies to the U.S. military overseas.
U.S. diplomats in Kenya and the U.S. Navy confirmed the vessel had been hijacked about 500 kilometres off the Somali coast.
Spokesman Lieutenant Nathan Christensen said the attacked happened in the early hours of the morning northeast of Eyl, a town in the northern Puntland region of Somalia. Lt. Christensen said there were U.S. citizens aboard the ship, but he did not say how many.
Maersk confirmed the ship had been seized. In a statement, the company said the Maersk Alabama "was en route to Mombasa, when it was attacked approximately 500 kilometres of the Somalia coast. Our initial concern is to ensure proper support and assistance to their families."
Only a few U.S.-flagged tankers and freighters remain, mostly in service between U.S. ports like the tankers that bring Alaska oil to the southern United States. But U.S. law requires that vessels available for charter by the military sealift command are registered in the United States and are crewed by Americans.
It was not known if the Maersk Alabama was on an MSC voyage when it was hijacked.
Although pirates have seized scores of ships - including several supertankers - off the notorious and ungoverned province of Puntland in Somalia, today's hijacking was the fist time a U.S. flagged and crewed vessel had been taken.
U.S., Canadian and other allied warships conduct anti-piracy patrols in the region but it is one of the busiest shipping lanes in the world and is criss-crossed with hundreds of vessels every day, many in headed for or bound from the Persian Gulf.
Washington has a carrier battle group in the region and special forces based in both Bahrain and Iraq. However, any military effort to recover the vessel and free the crew would be fraught with risk.
Maersk, a Danish company, has one of the world's biggest fleets of container ships. The vessel is the sixth to be seized within a week.
With files from Associated Press