A U.N-backed tribunal sentenced a member of the Hezbollah militant group to life imprisonment Friday for his involvement in the 2005 assassination of former Lebanese Prime Minister Rafik Hariri.

Salim Jamil Ayyash was found guilty in August of homicide and committing a terrorist act over the deaths of Hariri and 21 others in the attack on Beirut's waterfront.

“Mr. Ayyash participated in an act of terrorism that caused mass murder. His role was crucial to the success of the attack,” Presiding Judge David Re said. “The trial chamber is satisfied that it should impose the maximum sentence for each of the five crimes of life imprisonment, to be served concurrently,” Re added.

Hariri's assassination pitched Lebanon into what was then its worst crisis since its 1975-90 civil war, touching off years of confrontation between rival political and sectarian factions. Prosecutors had called for a life sentence for each of the five counts of which Ayyash was convicted.

On Friday, one of the trial judges, Janet Nosworthy, said the assassination “most probably had to have involved a state actor” and that the state “with most to gain from Mr. Hariri’s elimination most likely was Syria.”

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