PARIS - Centrist Emmanuel Macron solidified his status as front-runner in France's presidential election on Monday in a televised debate during which he clashed on immigration and Europe with his main rival, far-right leader Marine Le Pen.

A snap opinion poll showed Macron, a former economy minister who has never run for public office before, was seen as the most convincing among the top five contenders in a marathon debate of nearly three and a half hours that delivered no knockouts.

The debate, and the two others that will follow ahead of the April 23 first round, are seen as key in an election in which nearly 40 percent of voters say they are not sure who to back.

"You are failing (voters) by twisting the truth," Macron told Le Pen when she talked about a rise of radical Islam in France and said he was in favor of the burkini, a full-body swimsuit worn by some Muslim women that stirred much controversy in France last summer.

Later in the debate, National Front leader Le Pen mocked Macron, saying, of his comments: "It's completely empty. I want to attract the French people's attention to the fact that every time you talk, you say a bit of this, a bit of that, and never decide."

Opinion polls have for weeks shown Le Pen and Macron, an independent centrist who used to be Socialist President Francois Hollande's economy minister, pulling away from the pack in an election full of twists and turns which is taking place against a backdrop of high unemployment and sluggish growth.

Twenty-nine percent of viewers thought Macron was the most convincing, ahead of firebrand leftist Jean-Luc Melenchon with 20 percent, while Le Pen and conservative Francois Fillon were tied in third place, a snap survey conducted online by Elabe pollsters towards the end of the debate showed. Socialist candidate Benoit Hamon came in last.

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 Le Pen victory. She is pledging to take France out of the euro and hold a referendum on EU membership.

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