4 Americans killed by Somali hijackers aboard yacht (UPDATES) (VIDEO)

Four hostages on board a yacht hijacked by pirates last week were killed by their captors, U.S. Central Command said in a statement Tuesday.

The yacht SV Quest was hijacked on Friday off the coast of Oman, and officials had said Tuesday that it was less than two days from the Somali coast, according to CNN.

The U.S. Navy had said it was prepared to intervene to rescue the Americans — believed to be California couple Scott and Jean Adam, who own the yacht, and Phyllis Mackay and Bob Riggle.

GlobalPost senior correspondent Tristan McConnell reported that U.S. military negotiations to secure the release of the two American couples were under way when gunfire broke out aboard the 58-foot yacht early on Tuesday morning.

American soldiers deployed from a nearby warship responded to the shooting and fought their way aboard the Quest killing two pirates and capturing 13 others, McConnell reported. The remains of two other pirates who had died earlier were also found on board the boat.

“The forces discovered all four hostages had been shot by their captors. Despite immediate steps to provide life-saving care, all four hostages ultimately died of their wounds,” said the statement from the US military. 

“We express our deepest condolences for the innocent lives callously lost aboard the Quest,” said Gen James Mattis, commander of US Central Command in Florida.

The Quest had been taking part in international yacht race, but went off in a different direction on Feb. 15, according to the organizers of the race, the Blue Water Rally.

Somali pirates usually attack commercial ships instead of yachts. They have made hundreds of millions of dollars seizing merchant ships for ransom in recent years.

However, pirates held a British couple, Paul and Rachel Chandler, in Somalia for more than a year after seizing their yacht in October 2009.

International naval patrols off Somalia's coast have had little success in stopping pirates from attacking ships in the Gulf of Aden and Indian Ocean.

Pirates hijacked the Quest two days after a Somali pirate was sentenced to 33 years in prison by a New York court for the 2009 hijacking of the Maersk Alabama. That case ended in a spectacular rescue when Navy sharpshooters killed two pirates holding the ship's captain, Richard Phillips.

Estimates vary, but the pirates are believed to currently hold at least 31 vessels and about 700 hostages.