A French prosecutor says he will pursue attempted murder and terrorism charges against seven suspected radical Islamists who he says posed the biggest danger to France in years.

Francois Molins said Thursday the suspects were part of an active terrorist cell that was, as he put it,”probably the most dangerous in France since 1996.” At the time, Algerian Islamists carried out a series of bombings in France at the height of Algeria's civil war.

Molins also said the suspects planned to join “jihadists” fighting in Syria.

The seven suspects were among 12 arrested last week in raids in French cities, on suspicion of involvement in a grenade attack on a Jewish grocery store in September. Police say they found a list of Jewish institutions during a search of one of the suspect's homes.

On Wednesday, Molins said the nationwide police operation led to the discovery of bomb-making materials in a garage in a Paris suburb.

The materials included potassium nitrate, sulfur, saltpeter, pressure cookers and headlight bulbs — all products and instruments useful in the manufacture of improvised explosive devices.

French President Francois Hollande has vowed to boost security around synagogues and other Jewish buildings.

Five of the 12 suspects originally detained were released without charge on Thursday.