MOMBASA, Kenya - The U.S. and its allies battled Somalia's pirates on two fronts Wednesday, with French forces seizing a bandit mother ship and Washington seeking to keep the marauders from their spoils. Another U.S. freighter headed to port with armed sailors aboard after pirates damaged it with gunshots and grenades.

One pirate issued a new threat to "slaughter" Americans, and Tuesday's assault on a second U.S. cargo ship, the Liberty Sun, underscored the outlaws' ability to act with impunity despite international naval operations against them and mounting concern worldwide over how to end the escalating attacks off the Horn of Africa.

Pirates bombarded the U.S.-flagged Liberty Sun with automatic weapons fire and rocket-propelled grenades, but its American crew of about 20 successfully blockaded themselves in the engine room and warded off the attack with evasive maneuvers.

The ship, carrying food aid for hungry Africans _ including Somalis _ was damaged "pretty badly" on its bridge, a U.S. official said on condition of anonymity because he was not authorized to speak on the record about the ship.

Windows were blown out and the crew had to put out a small fire, the official said, but they were still able to navigate. By the time the USS Bainbridge arrived five hours later, the pirates were gone.

Meanwhile, French naval forces launched an early-morning attack on a suspected pirate "mother ship" 550 miles east of Mombasa and seized 11 men, thwarting an attack on the Liberian cargo ship Safmarine Asia, the French Defense Ministry said. No one was injured.

The ministry said the vessel was a larger ship that pirates use to allow their tiny skiffs to operate hundreds of miles off the coast.

French Foreign Ministry spokesman Christophe Prazuck said a French helicopter in the area heard a distress call from the Safmarine Asia. He described the seized ship as a small, noncommercial vessel carrying fuel, water and food supplies.

The 11 pirates, believed to be Somalis, were being held on the Nivose, a French frigate among the international fleet trying to protect shipping in the Gulf of Aden.

France has been proactive against pirates for at least the past year, intervening to save three of its ships and spearheading a Europe-wide anti-piracy force called Atalanta. French politicians have sought to have other European countries take greater action against pirates.

Three Somali pirates in the French city of Rennes faced judicial investigation after being captured in a hostage rescue Friday. Several other pirates also have been in French custody since last year.

In Washington, Secretary of State Hillary Rodham Clinton announced new diplomatic efforts to freeze the pirates' assets and said the Obama administration will work with shippers and insurers to improve their defenses against pirates, part of a diplomatic initiative to thwart attacks on shipping.

"These pirates are criminals, they are armed gangs on the sea. And those plotting attacks must be stopped," Clinton said at the State Department.

Clinton did not call for military force, although she mentioned "going after" pirate bases in Somalia, as authorized by the U.N. several months ago.

She said it may be possible to stop boat-building companies from doing business with the pirates.

The measures outlined by Clinton are largely stopgap moves while the administration weighs more comprehensive diplomatic and military action.

She acknowledged it will be hard to find the pirates' assets. But she wants the U.S. and others to "explore ways to track and freeze" pirate ransom money and other funds used in purchases of new boats, weapons and communications equipment.

"We have noticed that the pirates are buying more and more sophisticated equipment, they're buying faster and more capable vessels, they are clearly using their ransom money for their benefit _ both personally and on behalf of their piracy," she said. "We think we can begin to try and track and prevent that from happening."

Clinton said the administration will also call for immediate meetings of an international counterpiracy task force to expand naval coordination.

The U.S. plans to send an envoy to an April 23 conference on piracy in Brussels. The U.S. will also organize meetings with officials from Somalia's largely powerless transitional national government as well as regional leaders in its semiautonomous Puntland region to encourage them to do more to combat piracy.

Maritime experts say military force alone cannot solve the problem because the pirates operate in an area so vast as to render the flotilla of international warships largely ineffective. And with ships legally unable to carry arms in many ports, the world has struggled to end the scourge.

The Gulf of Aden, which links the Suez Canal and the Red Sea to the Indian Ocean, is the shortest route from Asia to Europe. More than 20,000 ships cross the vital sea lane every year. It is becoming more dangerous by the day.

In 2003, there were only 21 attacks in these waters. In less than four months this year, there have been 79 attacks, compared with 111 for all of 2008, according to the International Maritime Bureau.

Somali pirates are holding more than 280 foreign crewmen on 15 ships _ at least 76 of those sailors captured in recent days.

On Wednesday, pirates released the Greek-owned cargo ship Titan and Greek authorities said all 24 crewmen were in good health. The ship was hijacked March 19.

The assault on the Liberty Sun delayed a reunion between freed American sea captain Richard Phillips and the 19 crewmen of the Maersk Alabama he helped save in an attempted hijacking last week. Phillips had planned to meet his crew in Mombasa and fly home with them Wednesday, but he was stuck on the Bainbridge when it was diverted to help the Liberty Sun.

The Liberty Sun arrived safely in Mombasa Wednesday night accompanied by a U.S. Navy vessel, according to the cargo ship's operator, New York-based Liberty Maritime Corp.

The company did not name the the naval vessel, but it was likely the Bainbridge. A U.S. official who spoke on condition of anonymity because he is not authorized to speak to the press about the matter said earlier that the Bainbridge was traveling with the Liberty Sun to port.

The Alabama's crew left without Phillips Wednesday, heading to Andrews Air Force Base, Md., on a chartered plane.

"We are very happy to be going home," crewman William Rios of New York City said. But "we are disappointed to not be reuniting with the captain in Mombasa. He is a very brave man."

A pirate whose gang attacked the Liberty Sun claimed his group was targeting American ships and sailors.

"We will seek out the Americans, and if we capture them, we will slaughter them," said a 25-year-old pirate based in the Somali port of Harardhere who gave only his first name, Ismail.

"We will target their ships because we know their flags. Last night, an American-flagged ship escaped us by a whisker. We have showered them with rocket-propelled grenades," said Ismail, who did not take part in the Liberty Sun attack.

Pitman reported from Nairobi. Associated Press writers contributing this report include Mohamed Olad Hassan in Mogadishu, Somalia; Tom Maliti in Mombasa; Michelle Faul and Malkhadir M. Muhumed in Nairobi; Eliane Engeler in Geneva; Jenny Barchfield in Paris and Pauline Jelinek in Washington.

A service of the Associated Press(AP)