The two candidates -- right-winger Nicolas Sarkozy and Socialist Segolene Royal -- closed their campaigns Friday at midnight in accordance with election rules, and began steeling themselves for Sunday's vote.

Opinion polls were banned on the eve of the election, but all surveys taken since the April 22 first round have given a clear lead to Sarkozy -- with the gap widening in the last days of the campaign.

Some 44 million people can take part in the election, which offers a clear choice between two starkly different programmes of right and left.

Sarkozy, the 52-year-old head of the ruling Union for a Popular Movement (UMP), is proposing a radical economic agenda based on tax-cuts, limits to trade union powers and incentives to work harder.

Royal, 53, who is the first woman to have a serious chance of becoming French president, favours measures to safeguard the country's system of social protection and state intervention to create jobs.

The winner will take over from 74-year-old Jacques Chirac, president since 1995.

Both candidates are seen as representatives of a younger generation of politicians, promising new ideas to tackle France's runaway national debt, high unemployment and the festering discontent in high-immigration city suburbs.

Polling booths open at 8.00 am Sunday and close 12 hours later, with normally reliable projections due out immediately. Voting was taking place a day early in France's overseas territories in the Americas.

Sarkozy and Royal came first and second in the multi-candidate round of the election, with 31.2 percent and 25.9 percent of the vote.

The two-week second round campaign has focussed on the 6.8 million people -- 18.6 percent of the vote -- who chose the defeated centrist Francois Bayrou on April 22.

Bayrou has refused to give an endorsement to either candidate, though he has made it clear that his personal preference is for Royal. It was far from certain that his supporters would follow his lead.

The highpoint of the campaign was Wednesday's televised debate between Sarkozy and Royal, which was watched by some 20 million viewers.

Royal showed an unexpectedly aggressive streak in the head-to-head -- at one point accusing Sarkozy of "political immorality". Her attacks won high praise from supporters, but surveys subsequently showed most voters found Sarkozy the more convincing.

Continuing to trail in the polls, Royal launched a fierce personal assault on Sarkozy Friday, saying his election would provoke violence in the high-immigration suburbs that were the centre of riots in 2005.

Referring to his "dangerous candidacy," Royal said she had a "responsibility to issue an alert over the risks ... regarding the violence and brutalities that will be triggered across the country. Everyone knows it but no one says it. It is a kind of taboo."

Sarkozy responded that "never in the history of the Fifth Republic have such violent and threatening comments been heard. Saying that if you vote for a candidate there will be violence is simply to reject the right to democratic expression."

French newspapers Saturday were banned from reporting polls or comments by either candidate, but several noted the gloomy atmosphere inside Royal's camp.

Le Parisien newspaper said that Royal's campaign "is ending in a surreal ambience ... you can cut the atmosphere at PS headquarters with a knife."

The left-wing daily Liberation said that "the hypothesis of defeat began to take hold Friday. Only the candidate herself seems to keep the faith."