French police swooped in on suspected radical Islamists in pre-dawn raids in several cities on Wednesday, arresting at least 10 people, a source close to the investigation said.

The raids were notably carried out in the southern port city of Marseille as well as Roubaix near the Belgian border, and in several other locations in the country's south and southwest, the source said.

French authorities had announced a crackdown on Islamist extremists in the wake of a deadly shooting spree by a self-professed Al-Qaeda follower.