French nuns react in Saint-Etienne-du-Rouvray, near Rouen, France, during a tribute July 28, 2016 to French priest, Father Jacques Hamel, killed on Tuesday in an attack on the church that was carried out by assailants linked to Islamic State. [Photo/Agencies]

PARIS/SAINT-ETIENNE-DU-ROUVRAY, France - Police had been hunting the second teenager who killed a priest in a church in France this week after a foreign intelligence tipoff that a suspected jihadist might be preparing an attack, police and judicial sources said.

The revelation is likely to further fuel criticism by opposition politicians that President Francois Hollande's Socialist government did not do enough to stop the pair given that they were both already known to intelligence services.

They stormed a church service, forced a 85-year-old Roman Catholic priest to his knees at the altar and slit his throat.

They were later shot and killed by police.

Police had already identified 19-year-old Adel Kermiche as one of the attackers. He had made failed bids to reach Syria towage jihad, wore an electronic bracelet and was awaiting trial for alleged membership of a terrorist organisation having been released on bail.

They have now identified the second man as Abdel-Malik Nabil Petitjean, also 19, from a town in eastern France on the border with Germany, a judicial source said on Thursday.

A source close to the investigation said Petitjean was not known to French security services until a tipoff from Turkish authorities. He was stopped and questioned by profilers on his arrival at Istanbul's international airport on June 10 before he was allowed to continue on his way, a Turkish official said.

Turkey notified the French authorities in late June, the source said, and anti-terrorism officials opened up a special file, suspecting he had become radicalised. The government has said there are about 10,500 people with such so-called 'S files' related to potential jihadi activities in France.

But in the time it took security agencies in Turkey, awell-trodden entry point into Syria for foreign militants, tonotify France, Petitjean had returned.

"We know that he turned around and returned on June 11, "said the source. "The Turks hadn't yet flagged his name, so hecame back normally, there was no file at this point, he wasn't known to us."

A second tipoff from an unidentified foreign intelligence source led to the French authorities circulating a photo to its security agencies on July 22 of a man believed to be planning an attack. They had no name to go on, but the police sources said there was now little doubt that the photo was of Petitjean.

The person in the photo also appears to be one of a pair seen in a video posted on Wednesday by Islamic State's newsagency, the police sources said. The video claimed the two men were the church attackers and showed them pledging allegiance to Abu Bakr al-Baghdadi, Islamic State's leader.

Petitjean's mother Yamina told BFM TV that her son had never spoken about Islamic State.

A judicial source said that one man who had travelled to Turkey with Petitjean in June was among three people close to the teenager who were being detained in police custody.

Two opposition lawmakers on Thursday submitted a draft bill to parliament that would prohibit the media from publishing the identities and photographs of militant attackers to preventtheir names being glorified in death.