AFP - An American skipper held on a lifeboat by Somali pirates dived into the sea Friday in a dramatic break for freedom before being hauled back onboard, US networks said, as his captors demanded a ransom.
   
Captain Richard Phillips jumped into the water during the night and tried to swim towards the nearby US destroyer, the USS Bainbridge, but the pirates jumped into the water and recaptured him, three television networks reported.
   
The escape bid came as the pirates said they were demanding an unspecified amount of money for the skipper's release and warned against using force to secure his freedom.
   
US military officials told CNN that Phillips was fine, and that the pirates did not hurt him.
   
Phillips has been held hostage on the lifeboat since Wednesday when the gang of four pirates hijacked the Maersk Alabama aid ship. Although the pirates were later overpowered by the unarmed American crew, they were able to separate Phillips and bundle him onto a lifeboat.
   
The US navy has already encircled the lifeboat and more US ships, including from a counter-piracy task force out of Bahrain, are on the way to join the Bainbridge that arrived on Thursday, defence officials said.
   
The Bainbridge, accompanied by a P-3 Orion surveillance plane, was preventing the pirates from moving their hostage to a larger ship.
   
"The safe return of the captain is the top priority," Defense Secretary Robert Gates told reporters in Washington.
   
A commander of the pirates vowed that Phillips would remain a captive until a ransom was stumped up for his release.
   
"We are demanding to get ransom and to return home safely before releasing the captain," Abdi Garad told AFP by phone from Eyl, the pirates' lair in the largely lawless Somalia.
   
Garad also said their men were negotiating with the US navy "not to be arrested if they release the captain and the American officials will hopefully fulfil that condition otherwise the captain will not be released."
   
Meanwhile the Maersk Alabama headed to the Kenyan port of Mombasa with its cargo of aid destined for African refugees, US and company officials said. It was being sailed by US military personnel.
   
It had been due to dock in Mombasa on April 16 to deliver more than 5,000 tonnes of relief food supplies to the United Nations World Food Programme (WFP).
   
With six hijackings in the space of four days, Somalia's pirates have dashed any hope that increasing naval presence in the region could significantly dent a scourge that is disrupting one of the world's busiest maritime trade routes.
   
Since the start of the year, piracy watchdogs had recorded a slump in the number of attacks and their success rate compared to 2008, during which pirates attacked close to 150 ships and harvested a bumper crop of ransom money.
   
Hans Tino Hansen, managing director of Denmark-based Risk Intelligence, said one of the main reasons for the sudden surge in attacks was an improvement in the weather which allowed them to venture further out to sea.
   
"Due to the profile of the pirates’ skiffs and other vessels, they are very dependent on favourable weather conditions, which has been the case east of Somalia lately," he told AFP.
   
Analysts and military officers say pirate attacks are likely to grow given the lucrative ransom money paid by shipping companies and the lawless nature of Somalia.
   
Since April 4, Somali pirates have hijacked a US container ship, a small French sailing yacht, a British-owned Italian-operated cargo, a German container carrier, a Taiwanese fishing vessel and a Yemeni tugboat.
   
Some of the pirates' most spectacular successes came late last year when they seized a Ukrainian cargo loaded with combat tanks and other weaponry, as well as a Saudi super-tanker carrying 100 million dollars in crude oil.
   
The combined ransoms paid for the release of these two ships alone is believed to be around eight million dollars (six million euros) and the pirates are known to significantly reinvest in better equipment.