The top candidates in France's presidential election clashed in a televised debate with centrist Emmanuel Macron accusing far-right leader Marine Le Pen of lying and seeking to divide the French.

The debate, the first between the five main contenders ahead of a two-round election on 23 April and 7 May, could help viewers make up their minds in a French election where nearly 40% of voters say they are not sure who to back.

Opinion polls show Mr Macron and Ms Le Pen pulling away from the pack in an election that has been full of twists and turns, and which is taking place against a backdrop of high unemployment and sluggish growth.

One of the most heated exchanges came between the two frontrunners, after Ms Le Pen accused Mr Macron of being in favour of the burkini, a full-body swimsuit worn by Muslim women that created weeks of controversy in France last summer.

"You are lying (to voters) by twisting the truth," retorted Mr Macron, a 39-year-old former economy minister under Socialist President Francois Hollande who is running as an independent.

The debate grew testy when the candidates were asked about migration and Islam.

"I want to put an end to immigration, that's clear," Ms Le Pen said, before talking about a rise of Islamist fundamentalism in France and saying the security situation in France was "explosive".

After the surprise of Britain's Brexit vote and the election of Donald Trump in the United States, markets are nervous about the possibility of a Ms Le Pen victory. She is pledging to take France out of the euro and hold a referendum on EU membership.

While polls show Mr Macron and Ms Le Pen establishing a clear lead in the first round, conservative candidate Francois Fillon, the one-time front-runner, has fallen back, damaged by a scandal surrounding the employment of his wife as a parliamentary assistant.

Only the top two candidates go through to the runoff, where polls show Macron easily beating Le Pen.

But with so many voters undecided and polls showing the abstention rate could be higher than ever in France, the level of uncertainty remains high.

A high abstention rate could benefit Ms Le Pen as polls consistently show that her supporters are the most certain of their vote.