Somali pirates have seized a 31,000-tonne Malta-flagged grain carrier in the Gulf of Aden but the ship's 17 crew members are unhurt, a Kenyan maritime official said.

The MV Patriot is owned by Patriot Schiffahrts and managed by Blumenthal JMK of Hamburg, Germany.

"I hear it was taken early this morning," he told Reuters. "It was hijacked in the eastern end of the Gulf of Aden."

The Malta Maritime Authority said it had no information about the Polish Master, the Ukrainian Chief Engineer and the 15 Philippinos on board.

The Authority said it was in contact with the managers of the vessel and was liaising with various international authorities including the UKMTO Dubai co-ordination centre.

Piracy attacks off the eastern African coast have escalated in the past few weeks despite the presence of a flotilla of foreign navy warships in the region.

Sea gangs are holding more than 250 hostages and have made millions of dollars through ransoms, driving up insurance costs. Some shipping lines now opt to use a longer and more expensive route around the Cape of Good Hope to avoid capture.

Hijackings rose nearly 200 percent to 111 in 2008. So far this year, there have been about 40 incidents.

In the latest high-profile hijacking, pirates attacked a U.S. ship, the Maersk Alabama, earlier in April.

Its unarmed crew of 20 fought back and the pirates were forced to flee with the ship's captain, Richard Phillips, in a lifeboat. After a tense standoff with the U.S. Navy, Phillips was rescued, with three pirates shot dead by snipers.

The U.S. action could force the gangs to take more drastic action, including executing some of their hostages, some analysts say.

The pirates have so far avoided deliberately harming captured crew members and in 2008 secured some $100 million in ransom payments for crews and vessels.

The pirates have reinvested some of their takings in bigger weaponry and widened their reach to 500 miles (800 kms) from the Somali coast.