The arrests came as US Secretary of State Hillary Clinton announced a four-point plan to fight piracy that calls for broader interanational co-operation to prosecute pirates and freeze their assets.

The operation took place some 900 kilometers east of the Kenyan port of Mombasa when French sailors seized the 10-meter-long pirate mother ship, which had been carrying a large reserve of petrol and two "assault skiffs," the ministry said in a statement.

The 11 pirates were arrested and transferred to the French frigate, the Nivose.

They were first spotted late Tuesday when a helicopter from the Nivose helped ward off an attack on a freighter sailing under a Liberian flag. The helicopter then followed the attack boats back to the mother-ship.

Captain Christophe Prazuck said this was the ninth French operation against piracy in the past year and in total the navy had taken 74 suspects out of circulation, killing three and handing the rest to the relevant authorities.

Pirates caught after attacks on French nationals are brought back to France for trial, while others are handed over to African officials.

The Nivose is one of eight European warships taking part in Operation Atalanta, which is aimed at halting pirate attacks on private and commercial vessels in the Indian Ocean. German, Spanish and Italian forces are also involved in the EU operation.

US anti-piracy plan

Shortly after the arrests, the US Secretary of State told a press conference in Washington that the US would send an envoy to a Somali donors conference this week and seek a broader international effort to fight piracy off the Horn of Africa.

"We may be dealing with a 17th-century crime, but we need to bring 21st century assets to bear," Clinton told reporters at the State Department.

"Our envoy will work with other partners to help the Somalis assist us in cracking down on pirate bases and in decreasing incentives for young Somali men to engage in piracy," she said.

Greek release

In related news, a Greek freighter seized by pirates off the coast of Somalia four weeks ago has been released, Greece's state-run NET radio reported Wednesday.

The broadcaster quoted coast guard officials as saying the Titan was freed on Wednesday evening along with its crew of 24.

It was not clear whether the Greek owners of the vessel paid the pirates a ransom.

The release comes days after another Greek ship, the Irene EM, was taken over by pirates off the Somali coast.

More than 20 ships have been attacked in the last three weeks. Nine of those ships are in pirates' hands, bringing the total number of ships being held to 16. Almost 300 crew members are still being held hostage.