France went to the polls on Sunday to give its final verdict in the tense Presidential battle between right-wing incumbent Nicolas Sarkozy and his Socialist challenger Francois Hollande.

Opinion polls and electioneering were banned in the final 32 hours before polling stations opened at 8:00 am (0600 GMT), but Hollande began the day as firm favourite despite signs that Sarkozy was closing the gap.

More than 43 million voters were eligible to take part in France itself, after voting began on Saturday in the country's far-flung overseas territories. Polls were to close at 8:00 pm (1800 GMT), following immediately by initial results.

Hollande campaigned as a consensus-building moderate focused on restoring economic growth and is seen as on course to become France's first Socialist President since Francois Mitterrand died in office in 1995.

Sarkozy had trailed consistently in opinion polls for the previous six months, but fought a bruising campaign focused on mobilising voters fearful that immigration and globalisation threaten the French way of life.

Final opinion polls conducted on Friday before campaigning was officially suspended for the weekend suggested the still energetic Sarkozy may have closed the gap on the frontrunner to as little as four percent.

But a complete turnaround would still constitute a surprise, and Hollande was expected to assume the leadership of France, the eurozone's second-largest economy and a nuclear-armed permanent member of the UN Security Council.

Voter turnout in the first round of voting on April 22 was high, at around 80 per cent, and the duelling run-off candidates, both aged 57, have warned their supporters not to stay at home as every vote counts.

Hollande will vote in his provincial political heartland Tulle in central France, while Sarkozy was to vote in Paris' chic 16th arrondissement.

If he loses, Sarkozy will become the first French President since Valery Giscard d'Estaing in 1981 not to be re-elected. He was already the first ever incumbent not to come out ahead in the first round of voting.

France has a strict ban on publishing result estimates until all polls close, but foreign media websites are expected to publish estimates before then which will then spread via Twitter and Facebook.

Anyone breaking the law on publishing results estimates faces a fine of 75,000 euros (100,000 dollars), but French citizens got around the restriction in the first round by using code words and the Twitter hashtag #RadioLondres.

Hollande won the first round with 28.63 per cent of the votes to Sarkozy's 27.18 per cent, and both candidates have been fighting for the votes of those whose candidates failed to make the run-off.

Far-right anti-immigrant candidate Marine Le Pen, who won almost 18 per cent in the first round, has said she will cast a blank ballot and observers expect many of her supporters to do the same.

The polling institute Ifop, however, forecasts that 55 per cent of her voters would back Sarkozy and 19 per cent Hollande.

Hollande needs a strong mandate to implement his left-wing programme and fight EU-driven austerity, while Sarkozy has played on fears that the election of a Socialist would send shudders through the EU and the financial markets.

The last week of the campaign was marked by a dramatic television debate that saw the contenders trade insults without either landing a knock-out blow.

Many French were surprised at the Socialist's aggression, while Sarkozy defended his record as France's protector during a global economic crisis.

Fears over low economic growth, rising joblessness and European Union-imposed austerity measures have worked in favour of the Socialists.

Many voters also disapprove of Sarkozy's flashy style during his five-year term, welcoming Hollande's promise to be a 'normal President'.