Paris: Francois Hollande charged back into campaign mode on Monday with momentum on his side to capture France's presidency, after the Socialist won the most votes in the first round of voting that put him into a runoff with conservative incumbent Nicolas Sarkozy.

However, in the ballot's biggest surprise, nearly one in five voters chose far right candidate Marine Le Pen and they may hold the key to victory in the decisive vote on May 6.

If Hollande wins the second round, he would become the first Socialist president since 1995. His election could also alter Europe's political and economic landscape at a time when the continent is seeking a clear direction to overcome its calamitous debt crisis.

Polls taken Sunday night continued to show Hollande is likely to best Sarkozy in their head-to-head matchup two weeks from now by around 10 percentage points in line with the trend of most polls for months.

Both Hollande and Sarkozy resumed campaigning on Monday after a two-day pause to comply with election regulations that forbid campaigning from midnight Friday until 8 pm Sunday.

Sarkozy was headed to Tours in the Loire valley, while Hollande travelled to Quimper and Lorient in far-western Brittany.

Today Sarkozy suggested he'd be tacking at least somewhat to the right for the second round, in a bid to attract disgruntled National Front voters.

"National Front voters must be respected, they've expressed a choice. It's a vote of suffering, a vote of crisis. Why insult them?" Sarkozy said to reporters outside his Paris campaign headquarters. "I say to them, I've heard you. I'll draw all the consequences," Sarkozy said.

Turnout was surprisingly high, at more than 80 per cent, despite concern that a campaign focusing on nostalgia for a more protected past would fail to inspire voters.

The big shock of yesterday's vote: Nearly one in five voters chose far-right candidate Le Pen, handing her a solid third place and a chance to weigh in on French politics with her anti-immigration platform that targets France's millions of Muslims.

Political analyst Dominique Moisi pointed to the National Front's record vote as the surprise of the first round. "The strength of the populist extreme right shows that there is all over Europe a rise of populism as a result of the economic crisis."

Final results from the Interior Ministry showed Hollande had 28.6 per cent of the ballots cast and Sarkozy 27.2 per cent.

Le Pen was in third with 17.9 per cent, the best showing ever by the far right National Front party founded by her father Jean-Marie Le Pen. In fourth place was leftist firebrand Jean-Luc Melenchon with 11.1 per cent, followed by centrist Francois Bayrou with 9.1 per cent and five other candidates with minimal support.

Hollande, a 57-year-old who has worried financial markets with his pledges to boost government spending, vowed last night to cut France's huge debts, boost growth and unite the French after Sarkozy's divisive first term.

"Tonight I become the candidate of all the forces who want to turn one page and turn over another," Hollande told an exuberant crowd in his political fiefdom of Tulle in central France.

Sarkozy, speaking at his campaign headquarters on Paris' Left Bank, said he recognized voters' concerns about jobs and immigration, and "the concern of our compatriots to preserve their way of life."

Ten candidates faced off for Sunday's first round of voting, a referendum on Sarkozy at a time when many French voters are worried about high joblessness and weak economic prospects.

"Hollande should be happy. ... Sarkozy's objective was to beat him. It will be very difficult for Sarkozy now," said Damien Philippot of polling agency IFOP. "When you see the results it's clearly a vote of sanction for Nicolas Sarkozy."

Three French polls conducted Sunday evening as results came in predicted Hollande would win the May 6 runoff by 8 to 12 percentage points. Ipsos, CSA and IFOP said economic worries drove many voters.