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.

Mr Molins said the two men had been carrying a “fake explosive device covered in aluminium foil” along with hand-held weapons when they entered the Catholic church.

They took four people – some of them elderly parishioners – hostage along with 84-year-old Father Jacques Hamel.

Those who were able to escape alerted the police, who sent in a team specialised in dealing with hostage situations.

Three of the hostages were used as a barrier to block the police from entering the church, Mr Molins said.

When they were eventually let go, the two attackers followed them out of the church shouting “Allahu Akbar”, Mr Molins said.