The US captain taken hostage by Somali pirates managed to jump off their lifeboat overnight but was recaptured, according to US media reports.

The escape attempt by Capt Richard Phillips was witnessed by a US navy ship nearby but happened too fast for it to come to his aid, NBC News says.

He was captured after a struggle on his ship, Maersk Alabama. Pirates seized the ship but the crew fought them off.

There are thought to be four pirates with Capt Phillips in the lifeboat, which has reportedly run out of fuel, and it is not yet clear what they are demanding.

The Maersk Alabama is reportedly sailing for the Kenyan port of Mombasa under armed guard.

Gen David Petraeus, head of US Central Command, said reinforcements would arrive within 48 hours, adding that a warship was already very close to the lifeboat.

But other hijacked ships with hostages aboard are also reported to be nearing the area to support the pirates on the lifeboat.

The cruise-missile carrying USS Bainbridge was sent to the scene in a move analysts say will strengthen the hand of US negotiators.

The destroyer is shadowing the lifeboat, and its officers are talking to the pirates, as well as giving them food and batteries for a two-way radio.

Capt Phillips has a radio and contacted the navy and crew of his ship to say he was unharmed, the Maersk shipping company said in a statement.