PARIS - France's president has dismissed the far-right's use of a recent killing spree as evidence of a need for tougher immigration laws, saying Monday the call makes no sense in the wake of the massacre by a "monster" who was French-born.

Nicolas Sarkozy, facing a tough re-election campaign this spring, has veered to the right to garner votes, talking a tough line on immigration and the place of Islamic customs in France.

But he criticized one of his opponents on Monday -- National Front candidate Marine Le Pen -- for suggesting lax immigration laws led to the shootings of 23-year-old Mohamed Merah.

Last week, police tracked Merah to his apartment and after a more than 30-hour siege shot him dead as he jumped from a window, guns blazing.

Sarkozy has sought to paint Merah's killing spree, which left seven people dead in southwestern France in just over a week, as an isolated incident from which France shouldn't draw too many conclusions.

"We can't equate Mohamed Merah -- who was born in France, and is French -- with the children of immigrants who arrive by boat," Sarkozy told France-Info radio. "This Mohamed Merah, if you'll excuse me, was a monster."

Investigators are also looking into whether Merah's older brother, Abdelkader, helped in the killings of the rabbi, three Jewish children and three paratroopers. Abdelkader is in custody, and on Sunday was handed preliminary charges for complicity in murder and terrorism.

While Sarkozy rejected the link between the spree and immigration, he added that he still stands by his calls to tighten border controls, saying that France can't afford to provide benefits to illegal immigrants, and a flood of arrivals is overwhelming the country's means for assimilating newcomers.

This weekend Le Pen ramped up her rhetoric, promising to drastically reduce the number of immigrants coming to France's shores and warning that more such attacks await France if it does not shut its doors.

"How many Mohamed Merahs are in the planes and on boats that arrive each day in France filled with immigrants? How many Mohamed Merahs are among the non-assimilated immigrants?" she shouted to cheers at a rally in western France on Sunday.

Le Pen promised, if elected, to bring "radical Islam to its knees." Authorities said that Merah, during the standoff with police, told them he wanted to bring France "to its knees" with the spree that began in the city of Toulouse with the murder of a soldier.

It is not clear how the tragedy might affect the presidential election -- but Sarkozy made his name as a tough-as-nails interior minister and security is seen as one of his strong suits.

While 10 candidates are on the ballot for the first round vote in April, polls show the conservative Sarkozy and Francois Hollande, a Socialist, will qualify then for the decisive two-candidate runoff May 6. Hollande is presently leading in that second matchup.

France's security forces have been on the defensive for their handling of Merah's case -- with many wondering how a repeat juvenile offender known to police who ran in fanatical Islamist circles and had travelled to Afghanistan and Pakistan could have slipped through every net and been allowed to carry out such atrocity.

Sarkozy has acknowledged some errors.

"Slip-ups in our democracies exist, but we investigate them," he said.

In the wake of Merahs' slayings, Sarkozy has proposed new anti-terrorism measures, such as making it a crime to repeatedly visit Internet sites that promote terrorism, or travel to Afghanistan for the purpose of "indoctrination."

Sarkozy said Monday he will introduce the measures in Parliament after the election, if he wins.