NAIROBI, Kenya: Somali pirates seized a supertanker carrying crude oil from Saudi Arabia to the United States in the increasingly dangerous waters off East Africa, an official said on Monday, an attack that could pose a huge environmental or security threat to the region.

The Greece-flagged Maran Centaurus was hijacked on Sunday northeast of the Seychelles about 1,300 km off the coast of Somalia, said Cmdr. John Harbor, a spokesman for the EU Naval Force.

Harbor said it originated from Jeddah, Saudi Arabia and was destined for the United States. Maran Centaurus, with a crew of nine Greeks, 16 Filipinos, two Ukrainians and a Romanian, is a very large crude carrier, or VLCC. The shipping intelligence company Lloyd’s List said the ship has a capacity of over 300,000 tons. The tanker was headed for the lawless Horn of Africa state’s coast late Monday, a Kenyan maritime official told AFP. It was expected to arrive off Somalia’s coast Tuesday morning.

The pirates may anchor the huge vessel either off Hobyo or Harardhere — pirate dens in northern Somalia — the EU naval force Atalante said in a statement.

Pirates have increased attacks on vessels off East Africa for the millions in ransom that can be had. Though pirates have successfully hijacked dozens of vessels the last several years, Sunday’s attack appears to be only the second ever on an oil tanker.

The hijacking of a tanker increases worries that the vessel could crash, be run aground or be involved in a firefight, said Roger Middleton, a piracy expert at London-based think tank Chatham House.

Pirates typically use guns and rocket-propelled grenades in their attacks, and some vessels now carry private security guards, but Middleton said oil tankers do not. “You’re sitting on a huge ship filled with flammable liquid. You don’t want somebody with a gun on top of that,” Middleton said. “Financially it’s a very costly exercise because the value of oil is so volatile. If it is held for a long time and the price of oil drops, they could lost millions of dollars.” In November 2008, pirates hijacked the Saudi supertanker Sirius Star, which held 2 million barrels of oil valued at about $100 million.

The tanker was released last January for a reported $3 million ransom after a two-month drama that helped galvanize international efforts to fight piracy off Africa’s coast.

In late 2007, pirates hijacked a chemical tanker carrying up to 10,000 tons of highly explosive benzene. Initially, American intelligence agents worried terrorists from Somalia’s extremist insurgency could be involved, and might try to crash the boat into an offshore oil platform or use it as a gigantic bomb.

When the Japanese vessel was towed back into Somali waters and ransom demanded, the coalition was relieved to realize it was just another pirate attack.

Somalia’s lawless 3,000-km coastline provides a perfect haven for pirates to prey on ships heading for the Gulf of Aden, one of the world’s busiest shipping routes.

Meanwhile, the UN Security Council on Monday renewed authorization for measures to combat piracy off Somalia’s coast and warned nations against paying pirates ransoms to free hijacked ships. The 15 members of the United Nations council unanimously approved resolution 1897 extending anti-piracy measures for a year.

The resolution expresses the council’s concern “that escalating ransom payments and the lack of enforcement of the arms embargo... are fueling the growth of piracy off the coast of Somalia.”

Resolution 1897 gives foreign nations fighting piracy authorization through Nov. 30, 2010 to send warships into Somalia’s territorial waters, under an agreement with the Somali government.