French commandos arrested six alleged pirates in April
French commandos have freed two sailors seized by pirates off the Somali coast, the French presidency has said.
One pirate was killed in the operation and another six captured, it said.
The couple were seized in a sailing boat in the Gulf of Aden earlier this month by pirates who reportedly wanted a ransom of some $1.4m (£0.8m).
President Nicolas Sarkozy said the French operation should serve as a warning, and called for international efforts to counter escalating piracy.
The waters off Somalia, which is wracked by conflict, are among the most dangerous in the world. Attacks by pirates are common and hamper the delivery of food aid.
In the latest reported incident, a Hong Kong-owned tanker was seized late on Monday in the Gulf of Aden.
International Maritime Bureau (IMB) Piracy Reporting Centre told the AFP news agency that 22 crew members were taken hostage.
French commandos launched a similar raid against Somali pirates in April.
'Safe and sound'
President Sarkozy said the 30-man operation had taken just 10 minutes.
He said he had given the go-ahead late on Monday when it was clear that the pirates were heading for the lawless port of Eyl, where many well-armed pirate gangs are based.
He said it would have been too dangerous to free them if they arrived in Eyl, reports Reuters news agency.
A minister in the semi-autonomous Puntland region recently told the BBC that when he visited Eyl, he could see at least 10 boats being held by pirates there.
"The two French nationals are safe and sound," the French statement said.
Tahiti-based sailing enthusiasts Jean-Yves and Bernadette Delanne were on their way from Australia to France, through the Gulf of Aden, when they were captured on 2 September.
"This operation is a warning to all those who indulge in this criminal activity," Mr Sarkozy said at a press conference on Tuesday. "France will not allow crime to pay."
"I call on other countries to take their responsibilities as France has done twice."
Attacks against fishing boats, cargo ships and yachts have surged over recent months and foreigners, who can be exchanged for large ransoms, are frequent targets.
Warships from France and other nations have been patrolling the Somali coast to protect ships carrying aid to the country, where up to a third of the population needs food aid.
On Monday, European foreign ministers agreed to set up a "co-ordination unit" to improve security patrols.
France, which holds the rotating presidency of the European Union, has a military base in neighbouring Djibouti.
In April, French commandos made six arrests in a helicopter raid on Somali pirates after they had been paid a ransom to free the crew of another French yacht.
The six seized alleged pirates were handed over to French justice officials to be tried.
According to Reuters, the pirate group holding the Delanne couple were also demanding the release of their compatriots held in France.
Authorities in the semi-autonomous northern region of Puntland welcomed the French move.
Puntland's administration claims it is powerless in the face of the growing power of the pirates, who are well-armed and employ a lot of people.
"The state of Puntland encourages such steps and calls on other governments whose nationals are being held to do the same thing the French have done," Puntland presidential adviser Bille Mohamoud Qabowsade told AFP.
The IMB says pirates off Somalia use "mother ships" that travel far out to sea and launch smaller boats to attack passing vessels, sometimes using rocket-propelled grenades (RPGs).
Somalia has been without a functioning central government for 17 years and has suffered from continual civil strife.
Battles between Islamist insurgents and Ethiopian-backed government soldiers have forced hundreds of thousands of people from their homes in the last 18 months.