Five of the 12 suspects detained in a French crackdown on an alleged cell of Islamic extremists have been released and the others are due to appear before a judge on Thursday, a judicial source said.

The remaining seven suspects will be presented before an anti-terrorism judge to face as yet unspecified charges, the source said. Prosecutors are due to make a statement at 0830 GMT.

French prosecutors said Wednesday they were dealing with an "extremely dangerous terrorist cell" and had seized a significant amount of bomb-making equipment in their probe into the group.

The 12 were detained at the weekend in the southern city of Cannes and other areas on suspicion of involvement in a grenade attack on a Jewish grocery near Paris last month and of planning other anti-Semitic attacks.

One alleged leading member of the group, 33-year-old Jeremie Louis-Sidney, was shot dead Saturday after he opened fire on officers seeking to arrest him in a dawn raid at his home in Strasbourg.