Washington (PTI): The U.S. merchant ship captain, held hostage by pirates off the Somalian coast for the last five days, was freed unharmed today, with three of his four captors killed, a media report said.

Richard Phillips, the captain of the Maersk Alabama was freed today and is in "good condition," CNN said quoting a senior U.S. official.

While three of the four pirates holding him hostage were killed, the fourth pirate is in custody, the official said.

"Captain Phillips is uninjured and in good condition...The fourth pirate is in custody. Phillips was taken aboard a nearby naval warship," the official was quoted as saying by the CNN. Meanwhile, a family member of the captain confirmed the news.

Earlier, the U.S. Navy had sighted Phillips twice in a lifeboat where pirates were holding him, the Maersk Line Limited, owner of the Maersk Alabama ship, had said.

The FBI had on Saturday launched a criminal investigation into the hijacking by Somali pirates.

The Maersk Alabama was taken hostage by pirates earlier this week. However, the ship along with 19 American sailors was freed after Capt. Phillips offered himself as a hostage.

The ship reached the Mombasa port in Kenya early Sunday, without the captain.

An attempt by Capt. Phillips to escape from the lifeboat was thwarted by his captors earlier.