The 333-meter-long Samho Dream, which can carry more than 2 million barrels of crude oil, was hijacked and its crew of five Republic of Koreans and 19 Filipinos was taken hostage, RoK foreign ministry said in a statement.

U.S. refiner Valero Energy Corp said it was the owner of the crude oil cargo aboard the Samho Dream. The cargo was bound for the U.S. Gulf Coast, Valero spokesman Bill Day said.

A pirate source named Mohamed said the ship was now heading for Haradheere, the port and pirates' base at which many ships are held during ransom negotiations.

Increasingly brazen pirate activity has driven up insurance costs, forced some ships to go around South Africa instead of through the Suez Canal, and secured millions of dollars in ransoms.