A French court on Wednesday sentenced to jail terms of up to 13 years three men charged with connections to the brutal 2016 jihadist killing of an 85-year-old priest that shocked the country.

Father Jacques Hamel had his throat slit at the foot of the altar on July 26, 2016 at his small church in Saint-Etienne-du-Rouvray, a working-class suburb of Rouen in northwest France.

The two 19-year-old assailants, Adel Kermiche and Abdel-Malik Petitjean, also seriously wounded a worshipper after bursting in during mass and taking hostages before being shot and killed by police as they tried to leave the church.

They claimed in a video to be members of the Islamic State group, which later called them its "soldiers" retaliating for France's fight against jihadists in Syria and Iraq.

With the perpetrators dead, the three suspects on trial -- Jean-Philippe Jean Louis, Farid Khelil and Yassine Sebaihia -- were charged with "association in a terrorist act".

They had all been in contact with the assailants, with Jean Louis also travelling with Petitjean to Turkey just weeks before the attack in an attempt to reach Syria.

The Paris court sentenced Sebaihia to eight years in prison, Khelil to 10 years and Jean Louis to 13 years.

Father Jacques Hamel, 85, was conducting mass when two 19-year-olds burst into his church and slit his throat in 2016
Father Jacques Hamel, 85, was conducting mass when two 19-year-olds burst into his church and slit his throat in 2016 AFP / Sameer Al-DOUMY

The court ruled that even if they did not know the details of the plot, they were "perfectly aware that Adel Kermiche and Abdel-Malik Petitjean belonged to an association of criminals and were preparing a violent action".

The fourth defendant, Rachid Kassim, presumed dead in Iraq, was sentenced in absentia to life in prison for "complicity" in the killing.

Defendants are tried in France even if they are presumed -- but not confirmed -- to be dead.

Jean Louis, 25, was found to have run a Telegram channel in the area which played a central role in spreading jihadist ideas among youth.

Khelil, 36, was told he had consistently reinforced the determination of Petitjean, his cousin, to carry out an act of terror.

Sebaihia, 27, meanwhile had visited Kermiche two days before the killing and was found to have been aware of the killers' jihadist intentions.

The trial however was marked by scenes of reconciliation between the accused and relatives of the victim which have been almost unheard of in the legal processes over the spate of jihadist killings in France since 2015.

Khelil had earlier on Wednesday asked for forgiveness from the family, a move that the priest's sister Roseline Hamel said "had done a lot of good".

Ahead of the verdict, Roseline Hamel had also reached out to the four sisters of Jean Louis to comfort them and given a photo of her brother to each of the three accused.

Hamel's murder came as the country was on high alert over a series of jihadist attacks that began with a massacre at the satirical newspaper Charlie Hebdo in January 2015, which have claimed more than 250 lives.