One of the two attackers who stormed a church in France and slit a priest's throat on Tuesday had been charged with terror links and held before being freed on bail, a source close to the investigation said.

The assailant, who was known to France's anti-terrorism police, tried twice to go to Syria in 2015, the source told AFP. After his release, he had to wear an electronic monitoring bracelet that allows police to locate him at all times.