France's anti-immigrant National Front (FN) has surged to power in a former Socialist town-hall bastion and sees more victories in local elections where voters punished President Francois Hollande for failing to tackle unemployment.

In what leader Marine Le Pen called a breakthrough for her protectionist anti-EU party, the FN won power in the northern former coal-mining town Henin-Beaumont in a first-round vote on Sunday, and leads in at least six other towns before run-offs scheduled for next week.

With turnout levels at a record low of 65 percent after a series of political scandals that have hit mainstream French politicians of both left and right, Hollande's Socialists and their allies won just 38 percent of the national vote, behind 47 percent for opposition conservatives, initial tallies showed.

The FN won about five percent of the national vote - a proportionately high amount, given that it only fielded candidates in about 600 of the some 36,000 constituencies across France.

Prime Minister Jean-Marc Ayrault urged voters across the spectrum to back whatever candidate was best placed to beat FN rivals in Sunday's second round. A triumphant Le Pen said she was not interested in voter pacts with the mainstream right even if that could win her a greater presence on town hall councils.

"The National Front is taking root just as it wanted to do - and the crop is pretty exceptional," she told TF1 television.

Results released during the night put the National Front ahead in the eastern town of Forbach, in France's former industrial heartland.

In the south, the anti-EU party was in the lead in Avignon, Perpignan, Beziers and Frejus, and in second place in Marseille behind the conservative incumbent.

'Exceptional vintage'

The party's leader, Marine Le Pen, said the polls marked the "end of the bipolarisation of the political scene" and were "an exceptional vintage" for her party.

"The National Front has arrived as a major independent force - a political force both at the national and local level," Le Pen, who won 18 percent of votes in the 2012 presidential election, told TF1 television.

The party's Steeve Briois was declared outright winner to run the former northern coal-mining town of Henin-Beaumont, which has long been in Socialist hands.

Exit polls also put the National Front ahead in the eastern town of Forbach, in France's former industrial heartland. In the south, it was in the lead in Avignon, Perpignan, Beziers and Frejus and vying for second place in Marseille behind the conservative incumbent.

There was some solace for the Socialists as a TNS Sofres exit poll showed their candidate for Paris mayor, Anne Hidalgo, was ahead of her conservative rival Nathalie Kosciusko-Morizet.

The strong showing by the National Front will alarm Europe's liberal progressives, with the party long associated with racism and anti-Semitic statements.

Le Pen's father, Jean-Marie, was prosecuted several times while party leader for Holocaust denial, once referring to the deaths of millions of Jews as a "detail in the history of World War Two".

He has also been prosecuted for incitement to discriminate against Muslims.

Since becoming leader in 2011, Marine Le Pen has sanctioned or ejected party members found to have made racist comments in an attempt to make the party more palatable to French voters. Her policies focus on reduced immigration and take a stance against EU enlargement.