French counterterrorism agents — some heavily armed and wearing black hoods — raided homes and Internet cafes on Monday in a sweep against a suspected Islamic network, arresting more than 20 suspects, authorities said.

Ouassini Cherifi, a French-Algerian convicted in 2002 of trafficking phony passports, was among more than 20 suspects rounded up in the Paris area and the Oise region north of the capital on Monday, police said.

The sweep involving several hundred officers, including some who were heavily armed and hooded, was the largest of its kind in France in more than two years, said officials who spoke on condition of anonymity, either because their agencies demand it or because of laws that limit the release of information from investigations.

It also appeared to be one of the largest in Europe since Italian police arrested 28 Pakistanis in Naples after finding explosives in a rented apartment in January 2003. A judge later ordered their release, saying there was no reason to believe the Pakistanis knew explosives were hidden in the apartment.

Those arrested Monday included Tunisians, Moroccans, Algerians and French nationals, one official said. Some were known Islamic militants, others "common criminals" thought to have taken part in armed robberies and other violent crime.

"These two groups joined up, melted into each other," the official said. Some of those detained were women.

Counterterrorism agents had the alleged network under surveillance for months and believed some of its members intended to carry out attacks, although investigators have not determined when or where, the official added.

He said Cherifi met some members of the alleged network in prison. Cherifi was first arrested by France's Directorate for Territorial Surveillance counterterrorism agency in 2000 for trafficking phony French passports from Thailand that militants used to travel to the Pakistan-Afghanistan region and elsewhere.

Under French law, police have 96 hours to question the suspects.