A Paris court on Thursday sentenced three ex-members of the Palestinian group Abu Nidal in absentia to 30 years in prison for a 1988 attack on a Greek cruise ship in which nine people died.
The convictions were the first for the attack in which gunmen on the City of Poros opened fire on their fellow passengers as the ship, carrying hundreds of tourists, was on its way back to Athens after a day trip.
Judge Laurence Turbe-Bion handed down the verdict at the end of the case centred on the three men whose whereabouts are unknown and who investigators say may even be dead.
Three French nationals were killed in the attack, meaning a French court could handle the case.
Victims' lawyer Francis Szpiner said: "The message from this trial is that French justice never gives up on those who commit terrorist acts."
In the July 11, 1988 attack, at least one militant suddenly opened fire on fellow passengers with a machine pistol, before throwing a grenade and a firebomb, killing nine and wounding dozens.
The French dead were two students who had been due to get married and a 21-year-old secretary who had been playing cards with the main shooter before the attack.
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Greek police initially said that one of the French students was the shooter and that the secretary was his accomplice.
"The victims expect you to strongly condemn the infamy committed by the Greek authorities.. and that you recognise the dysfunctioning of French justice because of the time it has taken for a trial," lawyer Szpiner said during the trial.
Following the verdict, the court requested fresh arrest warrants for the three, two Lebanese and a Jordanian national.
If one day the men are arrested, a new trial must be held.
Around 30 witnesses identified a man in a photo named as Adnan Sojod as the main shooter, 21 years old at the time. Sojod was found guilty of murder, attempted murder and membership of a terrorist group.
Fellow militant Abdul Hamid Amud was jailed for helping him, as was Palestinian-born Jordanian national Samir Mohammed Ahmed Khaidir for organising the attack from Greece, Sweden and Libya.
Abu Nidal's group, believed to be responsible for a string of attacks which claimed at least 900 lives, notably in Europe, between 1970 and 1988, was for years on the US State Department list of terrorist organisations.
Abu Nidal died in Iraq in August 2002.