The South Korean-operated, Singapore-owned Samho Dream, which can carry more than 2 million barrels of crude oil, was hijacked on Sunday en route from Iraq to the United States, in the latest sign the sea gangs are targeting bigger quarry.

"The government has dispatched our Cheong-hae naval unit to the waters of the Indian Ocean, where the ship hijacked by Somali pirates is assumed to be," the Foreign Ministry said in a statement.

South Korea's anti-piracy Cheong-hae unit has a destroyer in the area to protect its commercial vessels. Local media said the destroyer, which can travel faster than the supertanker, would be able to reach the ship before it could reach any port.

The tanker's crew of five South Koreans and 19 Filipinos was taken hostage when it was seized about 1,560 kilometers east of the Somali coast.

"We can't reach the crew at all," said an official at SGSM, a subsidiary of Samho Shipping, which operates the tanker.

Texas-based refiner Valero Energy Corp said it was the owner of the crude oil cargo, which was bound for the US Gulf Coast.

"Asian importers including Korean will see little impact as their crude oil imports from the Middle East are moving in the opposite direction. US importers will have problems," said a trader at the country's biggest oil refiner SK Energy.

The 319,000 deadweight tonnage Samho Dream, which was built in 2002, is carrying crude oil that could be worth as much as $170 million at current oil prices.