PARIS (Reuters) - Three senior Syrian officials were found guilty by a French court on Friday of war crimes over their involvement in the disappearance and subsequent death of a French-Syrian father and his son.

All three were sentenced to life in prison, and people in the courtroom applauded the judges upon hearing the verdict. The trial was held in absentia.

The long-running case revolved around the disappearance and subsequent death of father Mazzen Dabbagh and his son Patrick, who were arrested by Syrian Airforce Intelligence agents in Syria in November 2013 and later died in custody.

"I feel very, very emotional. It was a verdict that I was waiting for. It's an historic trial, and one which will set a legal precedent for future cases," said Obeida Dabbagh, who was a brother to Mazzen and Patrick's uncle.

One of the officers found guilty of complicity in their disappearance and torture, Ali Mamlouk, is still in the Syrian security apparatus, as a security adviser to President Bashar al-Assad. The other two, Jamil Hassan and Abdel Salam Mahmoud, are a former director and director of investigation at the Airforce Intelligence unit.

None of the three accused attended the trial in the Cour d'Assises, which lasted four days.

The Syrian Information Ministry did not immediately respond to a request for comment about the ruling.

Syria's government, Assad and ally Russia have rejected accusations of mass killings and torture in a war that the United Nations has said claimed hundreds of thousands of lives.

Mazen Darwish, head of the Syrian Centre for Media and Freedom of Expression, which had been supporting the case, said it was the first to try a serving Syrian official.

(Reporting by Juliette Jabkhiro in Paris and Maya Gebeily in Beirut; Editing by Bill Berkrot)

By Juliette Jabkhiro and Maya Gebeily