By Ingrid Melander and Morade Azzouz
PARIS/HENIN-BEAUMONT (Reuters) - France voted in high-stakes regional elections on Sunday, just three weeks after deadly Islamic State militant attacks in Paris that could bring strong gains for the far-right National Front.
Security was boosted at polling stations in the capital, where militants killed 130 people by shootings and suicide bombs on Nov. 13, the worst attacks since World War Two.
The National Front (FN) may lead in as many as six out of 13 regions after the first round on Sunday. Voter participation among the 44.6 million people eligible to take part stood at 43.01 percent at 5 p.m. (1600 GMT), higher than the 39 percent five years ago.
"We're just in the first round, but we hope to have as big a lead as possible so the momentum is the strongest possible," National Front leader Marine Le Pen told Reuters TV after voting in the party's northern stronghold of Henin-Beaumont.
"I trust the voters because they have seen us work ... and that's why they are moving towards us," she said.
Like other anti-immigration, anti-Europe parties across Europe, the FN is also likely to benefit from worries over the refugee crisis to win at least one region, and possibly more, in a conclusive run-off on Dec. 13, opinion polls show.
Even winning one regional council would be a major victory for the FN which has never had control of such constituencies.
"After the Nov. 13 attacks we saw a clear increase in support for the National Front," Ifop pollster analyst Jerome Fourquet said. "Everything is adding up for (it) to make an unprecedented score."
The vote may reshape the political landscape, making French politics a three-way race as it gears up for 2017 presidential elections after decades of domination by the Socialists and conservatives.
"Too many don't come and vote and that lets extreme parties emerge, which I don't like," said 23 year-old Wandrille Launay, who was voting in Paris' 10th district not far from where the Nov. 13 attacks took place.
"In the last few days on social media I just saw so many things that shocked me, especially from people my age," he said.
STRATEGY SWITCH
The Socialists, who are now in power and control most regions, are set to lose most councils to either ex-president Nicolas Sarkozy's conservatives or the FN, despite a boost in President Francois Hollande's popularity ratings from his handling of the attacks.
Sarkozy, who just a few weeks ago was hoping for a landslide victory that would boost his chances for 2017, faces a smaller victory than expected for his Republicans party because of the FN's surging popularity, opinion polls show.
The key question as soon as polling stations close at 8 pm (1900 GMT) and results start trickling in will be whether the Socialists, seen coming third behind the FN and the Republicans in regions which the far-right could win over on Dec.13, will pull out of the race to try to keep them out of power.
The two regions where the FN is most likely to win are in the Nord-Pas-de-Calais region of northern France, where Marine Le Pen is a favourite, and the south-east, where her niece Marion Marechal-Le Pen is a leading contender. Participation in that region was almost 9 percent higher than in 2010 at 5 pm.
"This is a bad sign, because the National Front is becoming little by little more legitimate," Alain Alpern, a former Green and Socialist party local councillor, told Reuters outside an Henin-Beaumont polling station. "People don't realise what is in store for them."
Long content with attracting protest votes, the FN has changed strategy since Marine Le Pen took the party over from her father Jean-Marie in 2011, seeking to build a base of locally elected officials to target the top levels of power.
Voter turnout this Sunday and next will be key in regional polls that are usually spurned by about half the electorate both because of their complex two-round system and a lack of understanding of their role in France's multi-layered administrative structure.
French regions rule over local transport and economic development as well as high schools and vocational training, with beefed-up powers after a reform that cut their numbers from 22 to 13.
(Additional reporting by Morade Azzouz and John Irish; Editing by Richard Balmforth)
