French police commandos arrested 19 people and seized weapons in Friday morning swoops on people suspected of radical Islamist activity, in several cities including Toulouse, scene of the killings of four Jews and three soldiers this month.
President Nicolas Sarkozy, who is waging an uphill battle for re-election in an April-May vote, said more such raids would follow.
Sarkozy said in an interview with journalists that the trauma of the Toulouse shooting was "very deep in our country," NBC News reported.
He said it was "a bit -- I don't want to compare the horrors -- a bit like the trauma that followed in the U.S. and New York after 9⁄11."
"We cannot leave it without making any conclusions. The Minister of the Interior and the Minister of Foreign Affairs have taken the decision to forbid a certain number of predators on French soil .... We don't want people who have values contrary to those of the Republic being invited on French territory," Sarkozy added.
BBC News, citing a source, reported that the arrests were not connected with the killings of seven people by Mohamed Merah, a 23-year-old Frenchman, who was buried Thursday after he was cornered and shot dead by police.
Merah killed three Jewish schoolchildren, a rabbi and three French paratroopers in three separate attacks that revived worries about Islamist extremism and shook up the French presidential campaign.
The BBC noted that after Merah was killed, Paris prosecutor Francois Molins had said that accomplices were still being sought.
Reuters and The Associated Press contributed to this report.