Pirates near Somalia's coastline attacked a cargo ship Wednesday with a crew of at least 20 U.S. nationals aboard, according to the company that owns the vessel.
Maersk Line Ltd issued a statement saying it believes the U.S.-flagged Maersk Alabama was hijacked. If so, it would be the sixth hijacking over the past week in the region.
The container vessel was en route to Mombasa, Kenya, when it was attacked about 500 kilometers (310 miles) off Somalia's coast, the statement said.
U.S. government sources said the ship was attacked about 7:30 a.m., and the closest U.S. Navy warship was about 300 nautical miles away. On Tuesday, the U.S. Navy warned mariners that pirates were attacking ships hundreds of miles offshore.
The cargo ship is owned and operated by a Maersk subsidiary in Norfolk, Virginia, Maersk spokesman Michael Storgaard said.
He would not provide any details about the security arrangements on board the Maersk Alabama.
"We have very strict policies on the vessel ... crews are trained to handle these types of situations," Storgaard said from Maersk's headquarters in Copenhagen, Denmark.