French police have arrested a 21-year-old man in relation with the knife attack in a church in northern France, news channel BFMTV reported on Wednesday.

The man was arrested on Monday in Toulouse, southwest France, on charges of having contacting the two assailants who took hostage in Saint-Etienne-du-Rouvray and killed a priest last month, according to the report.

The suspect made a round trip between Toulouse and Saint-Etienne-du-Rouvray days before the attack, it added.

Three people have already been held into custody, including a Syrian asylum seeker and a minor, for the investigation into the attack.

On July 26, two young men took six hostages in a church in northern France, later slaughtered a priest and seriously wounded the other person. They were shot dead by the police.