France’s Interior Minister, Manuel Valls, has warned that the terror cell arrested this week after plotting an attack on a kosher grocery is just one of many.

Mr Valls’s warning came in the wake of a country-wide raid on a group of Muslim extremists whom police believe were responsible for planning a hand-grenade attack on a Jewish grocery in the Parisian suburb of Sarcelles on September 16.

The man alleged to have carried out the Sarcelles attack, a 32-year-old convert to Salafist Islam, Jeremie Félix Louis-Sidney, was shot dead when he opened fire on police raiding his flat in Paris last week. Twelve other members of Louis-Sidney’s cell were arrested simultaneously in Cannes, Torcy and in central Paris.

Police found an explosives laboratory, ammunition, 27,000 euros in cash, a list of Israeli organisations in Paris, Islamist manuals and antisemitic documents in the raids.

According to police reports, the ring had decided to launch “a war on France”, calling the killing of Jewish children and a teacher in the south of France in March, “the Battle of Toulouse”.

“Several other similar groups are being watched. There’s a real threat.

“We know that there are dozens, even hundreds of individuals who are capable of organising themselves like the group that has just been dismantled,” Mr Valls said in an interview on French television.

“Several other similar groups are being watched. There’s a real threat. Radical Islamism … thrives on fantasies, on hatred towards our country and towards French Jews.

Mr Valls added: “It’s all the more difficult to battle against these groups when they’re local. They’re not foreign terror networks that come from outside, but networks that have grown in our country, our neighbourhood. They’re not foreigners but French converts, French Muslims.”

A former head of a French intelligence agency told Ha’aretz that there are between 100 and 200 Islamic radicals who are potential terrorists.

French President François Hollande met representatives of the Jewish community on Sunday, assuring them that Jewish premises would be “secured”, especially during the festivals.

Mr Hollande said: “The government will work harder to fight terror… Nothing should be tolerated, nothing should be permitted” in the struggle to combat “racism and antisemitism”.

Richard Prasquier, the president of CRIF, the French Jewish umbrella group, said Mr Hollande was also concerned by the possible existence of several other terror cells.

Police put Louis-Sidney under close surveillance after his fingerprints were found on the remains of one of the grenades thrown into the Sarcelles shop.

Louis-Sidney came under the radar of French intelligence in March this year — the same month of the Toulouse murders — when he visited North Africa to meet imams, and started preaching radical Islam to younger Muslims.