NAIROBI, Kenya – A supertanker carrying about $160 million of crude oil from Iraq to the United States is believed to have been hijacked by Somali pirates, officials said Monday.

Similar seizures of oil supertankers in the waters off the coast of Somalia have yielded ransoms as high as $5.5 million.

A South Korean destroyer was rushing toward the supertanker, but its highly volatile cargo prevents crews from carrying guns on board or even lighting cigarettes while on deck.

The South Korean-operated 300,000-ton Samho Dream is believed to have been seized Sunday when the South Korean navy received a call from the vessel saying three pirates had boarded it. At the time, it was about 930 miles southeast of the Gulf of Aden. It has 24 crew members.

A maritime analyst doubted the South Korean warship would launch an assault on the pirates believed to be holding Samho Dream because such action would put the crew at great risk.

“The reason why an assault is extremely hazardous is you have to be able to suppress the pirates and take control back as fast as possible,” said Graeme Gibbon Brooks of Dryad Maritime Intelligence in Britain.