One of the attackers suspected of killing a priest at a church in north France was on probation and wearing a surveillance tag, officials say.

Prosecutor Francois Molins identified the suspect as Adel Kermiche, 19, who was twice arrested last year trying to reach Syria.

Kermiche and a fellow attacker stormed the church in Saint-Etienne-du-Rouvray, a suburb of Rouen, during morning Mass.

They slit the throat of the elderly priest before being killed by police.