Washington: Three Somali men pleaded guilty on Friday to piracy charges related to the hijacking of a yacht off the coast of Oman in February that left four Americans dead.
Mohamud Hirs Issa Ali, 32, and Mohamud Salad Ali, 35, and Ali Abdi Mohamed, 35, pleaded guilty in a federal court in the eastern state of Virginia, according to US prosecutors.
The owners of the yacht Quest, Jean and Scott Adam, were Christian missionaries based in California who were sailing around the world at the time of the hijacking.
They were shot to death, along with their companions Bob Riggle and Phyllis Macay from Seattle, Washington, several days after being taken hostage and as negotiations were taking place with US Navy officials.
Issa Ali and Salad Ali pleaded guilty to acts of piracy and hostage taking resulting in death, as part of plea agreements that will allow them to avoid the death penalty. They face life in prison.
The two men "acknowledged in connection with their pleas that they served as leaders of the piracy operation," prosecutors said in a statement.
The third man, Abdi Mohamed, who also made a plea deal, acknowledged "that he fired a rocket propelled grenade in the course of the crime”. He pleaded guilty to piracy. He also faces life in prison.
"All three defendants warranted in their plea agreements that they played no role in the murder of the four US citizens," the statement said.
Plea deals allow defendants to seek reductions in their sentences.
"He avoids death with the plea," Jon Babineau, lawyer for Issa Ali, said.
Eight other suspects in the case were also expected to plead guilty on Monday.
Accused Somali pirate Mohammad Saaili Shibin, said to have been the chief negotiator in the hijacking, was indicted on charges related to the killings earlier this year.
US service members, who had been trailing the yacht during the hostage drama, boarded the vessel after hearing gunshots and discovered the Americans` bodies, according to US officials.
The US military said it had undertaken negotiations, led by Shibin, to secure the release of the hostages at the time the pirates fatally shot their captives.
At the time of their arrest, the pirates were said to have been in possession of heavy weaponry, including a grenade launcher and several assault rifles.
The men are among 15 people -- 14 from Somalia and one from Yemen -- arrested after the attack for their roles in the kidnapping and killings.