MOMBASA, Kenya — On another day of high drama in the waters off Somalia, French forces struck Wednesday at what they described as a pirate "mother ship," and captured 11 suspected pirates hours after pirates attacked an American cargo ship with rockets in the second serious attack on a U.S. vessel in a week.

Pirates operating from the coast of Somalia have threatened revenge and stepped up their activities after U.S. Navy SEAL snipers killed three pirates Sunday and rescued American captain Richard Phillips, who'd been taken hostage. His ship, the Maersk Alabama, narrowly escaped capture a few days earlier.

In the Wednesday attack, pirates used automatic weapons and rocket-propelled grenades against the U.S.-flagged vessel, the Liberty Sun, which like the Alabama, was ferrying food aid into East Africa. They caused damage but no injuries and failed to seize the vessel. The crew barricaded itself in a safe room, much as the Alabama's crew did, according to a crewmember's e-mail obtained by news agencies.

In Washington, senior aides to President Barack Obama met at the White House Wednesday morning to a plan strategy to deal with the crisis and to address the chaos in anarchic Somalia that's part of the problem.

After the meeting, Secretary of State Hillary Clinton announced several new steps, including aid to shippers and insurers to bolster their defenses; attempts to block pirates from buying sophisticated vessels and arms; and a diplomatic initiative to press Somali leaders to deal with the problem.

Clinton acknowledged that piracy will not be stopped without tackling Somalia's poverty and its lack of governance. She said, however, that, "You've got to put out the fire before you can rebuild the house. And, right now, we have a fire raging."

The French raid was an unusually aggressive move by international forces patrolling the Indian Ocean, and it was a sign that both pirate attacks and the international response are escalating.

After a Liberian-flagged container ship came under heavy rocket-propelled grenade and small-arms fire from two pirate speedboats, a French frigate, the Nivose, dispatched two helicopters to the scene, about 500 miles east of the Kenyan port of Mombasa, the French defense ministry said. The helicopters saw the skiffs operating with a 30-foot "mother ship" — often a previously seized vessel used by pirates as a floating base.

Eleven pirates were captured and taken aboard the Nivose.

The assault was the latest hardline French response to piracy, following a commando raid last week to free a French yacht, the Tanit, in which French troops killed two pirates and one French hostage. They captured three other pirates, who've been sent to France, where they're expected to face trial, French officials have said.

The Liberty Sun was due to arrive in Mombasa, its original destination, early Thursday.

The captain of the Alabama, Richard Phillips, who was held hostage for five days, was also due in Mombasa Thursday aboard the destroyer USS Bainbridge. Phillips is to be questioned by U.S. law enforcement agents based in Kenya and then will fly to the U.S. to reunite with his family, said Gordan Van Hook, a representative of the ship's owner, Maersk Line of Norfolk, Va.

The 19 other Alabama crewmen flew out of Mombasa and were expected to reunite with their families at Andrews Air Force Base in Maryland, Van Hook said.

Clinton said she'd called for a meeting of an international "contact group" that deals with piracy from Somalia and would press for "an expanded multinational response."

A team of U.S. diplomats, she said, would engage officials of the weak Somalia government and regional leaders in Puntland, the breakaway Somali region where many pirates are based, to urge them to take action.

A State Department official, who requested anonymity to speak more frankly, said most of the steps Clinton announced drew from initiatives already under way and begun in the final days of the Bush administration.

Piracy will not be gotten under control until its root causes are dealt with, he said. "The real problem is that you have this huge swath of coastline which is essentially ungoverned, and which has no economy."

(Strobel reported from Washington.)

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