The U.S. Navy has stepped up its force of warships off the coast of Somalia closely monitoring pirates holding a hijacked Ukrainian-operated vessel with crew members, arms and tanks aboard.

Andrew Mwangura of the East Africa's Seafarers Assistance Program said on Monday three warships have surrounded the MV Faina that was seized on Thursday, with its 21 Ukrainian, Russian and Lithuanian crew members and an arms cargo that included 33 T-72 tanks.

"The American destroyer USS Howard is still waiting for reinforcement from Russia but has surrounded the Somali pirates," Mwangura told Xinhua by telephone.

But one of the pirates said they were not afraid and had enough food to withstand a siege. Maritime experts said the ship was carrying "dangerous chemicals" and warned against using force.

Lt. Nathan Christensen, a spokesman for the U.S. Navy Fifth Fleet, reportedly said "there are now several U.S. ships" within eyesight of the hijacked ship, which according to the Kenyan government was bound for Kenya when it was seized last week.

Christensen said the USS Howard was within eight kilometers of the Ukrainian vessel, but refused to say whether they were preparing to attack the pirates.

He said the ship's cargo of battle tanks made it a particularly worrying situation.

"We're concerned that this might end up in the wrong hands, such as terrorists or violent extremists," he said.

Islamist insurgents, not known to have links to the pirate gangs, are battling government troops, their Ethiopian allies and African Union peacekeepers in the capital, Mogadishu.

Mwangura said U.S. military helicopter had flown over pirate speedboats heading to reinforce the Ukrainian-operated ship surrounded areas near the town of Hobyo.

"With the helicopter and the Howard watching them, the tactic is clearly to scare the pirates but I don't know their (U.S. Navy) intention," said Mwangura.

Kenya said the tanks and weapons were for its military. Pirates have anchored the hijacked vessel a few miles off the Somali town of Hobyo.

Radio France International said Monday it had spoken, apparently by mobile phone, with a pirate aboard the Faina, who said at least three warships were near the hijacked ship.

"Ships and troops have surrounded us," said a man identified by RFI as pirate Sugule Ali. He spoke in Somali.

"There's a lot of unusual movement surrounding us and planes are flying overhead. I warn anyone who might be tempted by any military operation or use of force, if we're attacked, we'll defend ourselves, until the last one of us dies."

Faina is owned and operated by Kaalbye Shipping Ukraine, and its crew includes citizens of Ukraine, Russia and Latvia.

U.S. officials said the ship reported being surrounded by three small boats of pirates while sailing 250 miles off the coast of Somalia

The latest hijackings are part of a surge of daring maritime attacks off the coast of Somalia, a war-torn country that has been without a functioning government since 1991.

Authorities in Somalia's semi-autonomous region of Puntland say they are powerless to confront the pirates, who regularly hold ships for ransom at the port of Eyl.

There were reports that at least 100 pirates from the dreaded Somalia Youth Coast Guard were in control of the Faina, which is sailing under a Belize flag.

Pirates have seized dozens of ships near Somalia's coast in recent months.

(Xinhua News Agency September 30, 2008)