Fourteen Islamist militants, members of the Abu Sayyaf terrorist group, were convicted on Thursday by a Philippine court for the kidnapping of 20 people off an island resort in 2001. Among those kidnapped there were a U.S. missionary couple and another American, who where eventually killed.

Out of the 18 people who were at the Manilla courthouse, 14 received a sentence of life imprisonment. Four others were acquitted, including Abu Sabaya’s siter, Satra Tilao, the New York Times reports.

Robert Courtney, a Department of Justice attache at the United States Embassy in Manila, said: “It sends a strong message about the capability of the Philippine law enforcement to deal with terrorist activities through the criminal justice system.”

Sabaya was killed in 2002, after he held some of the hostages for 13 months, in a military operation supported by the U.S.

The operation was in order to rescue the three Americans, Martin and Gracia Burnham, a U.S. missionary couple, and Guillermo Sobero, a Peruvian-born American from California.

They were taken hostages on the night of May 27, 2001 by Abu Sayyaf gunmen who kidnapped them along with other 17 people from the Dos Palmas resort, on Palawan Island in the southwestern Philippines. The Burnhams were celebrating their 18th wedding anniversary and Sobero was on his holiday with his Filipina girlfriend.

He was beheaded just a few weeks after being kidnapped, Guardian Unlimited informs.

Mr. Burnham and a Filipino nurse, Ediborah Yap, were also killed a year later during a failed attempt to rescue them.

Mrs. Burnham survived after being shot in a leg. She wrote a controversial book regarding her experience there, in which she accused the military for helping the militants.

Thousands of American troops were sent to the Philippines after the Sept. 11, 2001, to help fight Abu Sayyaf, a terrorist group. It mainly operates in the southern Philippines.

An army spokesman, Lieutenant Colonel Ernesto Torres, said: “This is a triumph of justice, another battle won in our fight against terrorism. This is a source of encouragement for our soldiers in the front lines.”

Hostages were taken on speedboats to the islands of Jolo and Basilan.

Some of the hostages were freed after they paid ransom.

Initially 85 suspects were charged in the kidnapping. Only 23 were caught and put on trial in 2003. Four of them died when they tried to escape in 2005 and one was acquitted.