Nicolas Sarkozy (L) and his wife Carla Bruni-Sarkozy leave on April 22, 2012

France has gone to the polls on Sunday for the first round of a presidential election which could see Nicolas Sarkozy ejected from office.

Officials have reported a strong turnout in the early voting, with the Interior Ministry reporting 70% of all votes cast before 5pm. Local media said that around 80% participation was expected by the time polls close in large cities.

On Twitter French voters used a satirical search term, '#radioLondres', to get around extremely stringent laws prohibiting the publication of exit polls or other surveys before voting ends.

Anyone leaking the results would face a fine of up to $100,000.

The #RadioLondres topic, the name of which references foreign radio broadcasts from World War Two, highlighted pranksters jokingly referring to the price of maple syrup in two countries as code for the results.

Up to 44m people will vote in the election, including thousands of French people living in London, where long queues were reported at polling stations around the city.

Sunday's poll will see an initial list of 10 candidates cut down to two before a 6 May runoff contest - unless one candidate receives more than 50% of the vote.

Centre-right incumbent Sarkozy is facing a strong challenge from Socialist nominee Francois Hollande.

Polls have shown that Sarkozy is likely to make the cut with Hollande, despite the potential for a shock result.

In the 2002 election right-winger Jean Marie Le Pen ousted Lionel Jospin from the second-round, leading to an easy win for Jacques Chirac in the second round.

Sarkozy's popularity has fallen in the past few weeks, with voters said to be looking for hard solutions on jobs and economic growth.

Hollande has promised to raise the minimum wage while raising corporation tax and levies on high earners. He has also pledged to hire more teachers and lower the retirement age for some workers to 60.

Sarkozy has pledged to tackle immigration by pulling out of the "passport free" zone unless other countries do more to reduce numbers of illegal migrants entering the EU. He has also campaigned on reducing France's defect and promoting economic growth.

Sarkozy has been in office since 2007, and if he loses would be the first president since 1981 not to receive a second term from French voters.

Both main candidates have pushed for a strong turnout, the AP reported, in order to dilute the impact of fringe candidates including far-right nationalist Marine Le Pen, daughter of the 2002 second-round contender.

The eventual result could have massive repercussions for Europe, given Sarkozy's strong support with German Chancellor Angela Merkel for budget austerity in the eurozone.

Hollande has said that a new treaty in the eurozone will also have to help states support economic growth through spending.