In a continuing display of firmness against terrorism, President Nicolas Sarkozy announced Friday that police had rounded up 19 Islamic activists and discovered several assault rifles in early-morning raids in Paris and two other French cities.

The raids, carried out by paramilitary anti-terrorism commandos, were part of a crackdown imposed by Sarkozy after a young French extremist of Algerian origin, Mohammed Merah, shot dead seven people this month in the Toulouse region before being killed himself in a March 22 shootout with commandos.

Sarkozy’s show of determination against Islamic extremism has been criticized as a calculated bid to boost his standing in the campaign for a two-round presidential election scheduled for April 22 and May 6. Sarkozy, running for a second five-year term, has begun to pull even with his main adversary, Francois Hollande of the Socialist Party, after months of trailing in the polls. But the ultra-right National Front candidate, Marine Le Pen, has attacked Sarkozy for being lax on immigration.

Immediately after Merah was killed, Sarkozy announced he would propose a panoply of anti-terrorism laws for swift enactment, including a provision that would make it a crime to look at extremist Islamist Web sites. Since then, however, his aides have pointed out that Parliament has suspended work during the election campaign, putting the proposals into doubt, and others have questioned the constitutionality of such legislation.

During a radio interview, Sarkozy said the 19 taken into custody Friday were not directly linked to the Toulouse killings but were adherents of “a form of radical Islam” that would not be tolerated in France. He did not say what laws they were suspected of violating but suggested that at least some of them would be expelled. Sarkozy said the raids were carried out “in full accord with the justice system.”

Seventeen of those detained were held for questioning, while two were released, authorities announced.

“What happened this morning is going to continue,” Sarkozy said. “There will be other operations that will continue and that will allow us to expel from the national territory people who have no business being here.”

With police cooperation, some of the arrests were filmed for broadcast on television news programs.

Interior Ministry officials told French reporters that the detainees were part of an outlawed group called Forsan al-Izza, which is centered in the Nantes area but has followers in the Toulouse and Paris regions.

The raids followed an announcement Thursday that the government would refuse visas to four Islamic preachers invited to a convention of the Union of Islamic Organizations of France, which officials described as sympathetic to the fundamentalist Muslim Brother­hood. The four were identified as Adrima Sabri, a Palestinian; Ayad bin Abdallah al-Qarni and Abdallah Basar, Saudi Arabians; and Sawfat al-Hijazi, an Egyptian.

“The positions and statements of these people, who call for hatred and violence, seriously undermine the principles of the republic in the current context, raising a strong risk of troubling public order,” a joint communique from the Foreign and Interior ministries said.

Two other invitees canceled plans to attend after it was made clear they were unwelcome. They were Youssef Qaradawi, a renowned Egyptian preacher who resides in Qatar and appears regularly on al-Jazeera television, and Mahmoud al-Masri, an Egyptian.

A seventh preacher and theologian whom officials characterized as undesirable, Tariq Ramadan, has Swiss nationality and thus could not be banned under European Union accords with Switzerland. It was unclear whether he planned to attend.

Sarkozy said he had called the emir of Qatar personally to ask that Qaradawi be prevented from coming to France, adding, “This gentleman is not welcome in the territory of the republic.”

Merah, meanwhile, was buried Thursday in an informal ceremony in a Toulouse suburb attended by several dozen young people but without his family present. His father had sought to have him transported to Algeria for burial in the family’s village there, but the Algerian government refused to accept it.