SAINT-ETIENNE-DU-ROUVRAY, France, July 26 (Reuters) - Knife-wielding attackers interrupted a church service in France, forced the priest to his knees and slit his throat on Tuesday, an attack that President Francois Hollande said showed the threat from Islamist militancy was greater than ever.

Police shot and killed the attackers as they emerged from the church, freeing three hostages, one of whom was seriously wounded.

One of the knifemen was identified as 19-year-old Adel Kermiche, who was under close surveillance after two failed attempts to reach Syria last year, Frances anti-terror prosecutor said.

After the last attempt in May, 2015, Kermiche, who was from the Normandy town where the attack took place, was detained until March. He was then released but forced to wear an electronic tag to track his whereabouts and was allowed to only leave his home for a few hours a day, prosecutor Francois Molins said.

Police were still seeking to identify the second of the two attackers and raids were underway, Molins told a news conference.