A terror plot to attack A military base and decapitate its commander has been foiled in France, as reported by prosecutors.

French news agency AFP quotes an anonymous source by saying the suspects had been planning to film the decapitation of a member of the military.

One of the group, 23-year-old Djebril A, had served as a naval signalman at the military post Fort Bear on the southern French coast.

Cazeneuve confirmed that the teenager came to the attention of French intelligence in 2014 after monitoring his conversations with French jihadis on social media, where he expressed a desire to travel to Syria.

Ismael, who had learned of the surveillance after being interviewed by officials, engaged in “encrypted messaging” with the ISIL member.

The prosecutor of Aix-en-Provence, Dominuqe Moyal, later confirmed on BFMTV that an official investigation was underway and said “material had been found near the explosions”, which affected two storage tanks.

“At the (Bastille Day) ceremony, the President reminded us that every week we prevent… terrorist acts”, Cazeneuve said.

Security forces in France have foiled attacks on a military installation with the arrests of four people allegedly linked to militant groups, President Francois Hollande said Wednesday.

Thibault-Lecuivre said the youngest of the suspects had been released from custody as of Thursday.

No link has been made at this point between the people detained and explosions this week at a petrochemical plant in southern France, Cazeneuve said. “The first indications show that we are dealing with a criminal act, but no motive has been established”, Mr Cazeneuve told the lower house.

Cazeneuve said Wednesday that 1,850 French citizens or people who usually reside in France are implicated in jihadist networks, including close to 500 individuals now in Syria or Iraq.

France, which is home to Europe’s largest Muslim population, has beefed up security, posting 30,000 police officers and soldiers outside 5,000 sites deemed “sensitive” such as schools and places of worship.

The authorities have also set up a hotline for friends or family concerned that someone could be tempted to wage jihad – an effort that has yielded 2,500 leads.

Following controversial “anti-terror” laws passed a year ago, France is also preventing suspected militants from leaving the country – a few 118 travel bans have been enforced since the legislation was passed in November.