French police have thwarted five attacks, including a suspected plan to target church-goers foiled in recent days, since the Islamist killings at a satirical weekly and Jewish food shop in January, Prime Minster Manuel Valls said yesterday.

“Never has the threat been so high,” Valls told France Inter radio, noting the fact that hundreds of French nationals were now in Syria where they risked being radicalised.

Valls was speaking a day after authorities said they had arrested a 24-year-old Algerian national in Paris suspected of the murder of a woman at the weekend and an aborted plan to launch an armed attack on at least one church.