We have to defend this France and not the France that Le Pen likes

Pierre, a demonstrator

Organisers said 30-45,000 people in Paris and more than 100,000 nationwide turned out to protest at the National Front (FN) leader's shock election success.

Demonstrators marched towards the Place de la Bastille shouting "Down with the National Front."

The police estimated that some 20,000 people took to the streets in protest in the Alpine town of Grenoble and 15,000 in the southern port of Marseille, regarded as a stronghold of Mr Le Pen.

'Danger for democracy'

The BBC's Jamie Coomarasamy says there was a carnival spirit at the demonstrations but also a mood of determination.

"This time there's a real danger for our democracy," said one demonstrator, who refused to accept the standard view that incumbent Jacques Chirac would beat Mr Le Pen by a landslide.

	:	Voters' voices
In pictures: French voters have their say

Pierre, who came to the rally with his Tunisian wife, pointed to his mixed race son when asked why he was demonstrating.

"Look at him, that's the only answer," he told the BBC. "We have to defend this France and not the France that Le Pen likes."

Clashes feared

Paris police chief Jean-Paul Proust has announced extra security measures ahead of a climax of protest expected on 1 May.

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Around 3,000 police will be deployed in the capital on Wednesday, when clashes are feared as supporters of both candidates mass for rival Labour Day rallies ahead of the 5 May presidential run-off.

	Jean-Marie Le Pen Born in 1928 in the Brittany town of La Trinite-sur-Mer Set up the National Front in 1972 In 1987 he described the Holocaust as a "detail of history" Wants 200,000 new prison places, the abolition of inheritance tax and a renegotiation of European treaties  Click here for a full profile

Saturday's protests come a day after the far-right leader railed against immigrants, in a speech diverging from his initially moderate post-victory rhetoric.

Mr Le Pen said that if he became president he would have asylum seekers put in "transit camps" before expelling them.

At a news conference on Friday, Mr Le Pen said that camps for asylum-seekers already existed in the US and that his ideas were "no more racist" than those of British Prime Minister Tony Blair.

He added that a "special train" might be sent to Britain carrying asylum-seekers from the controversial holding centre at Sangatte.

A spokesman for Mr Blair immediately condemned the comparison, saying the FN leader was trying to exploit a "serious issue".

The head of the French anti-racist group MRAP, Mouloud Aounit, described Mr Le Pen's use of the word "camps" as "totally obnoxious", saying it harked back to Nazi concentration camps.