Paris: Centrist presidential frontrunner Emmanuel Macron and his far-right rival Marine Le Pen attacked each other's visions of France and the role it should play in Europe on Monday against a background of May Day rallies and protests.

Macron sought for a third successive day to paint National Front (FN) candidate Le Pen as an extremist, while she portrayed him as a clone of unpopular outgoing Socialist President Francois Hollande, under whom he served as economy minister from 2014 to 2016.

Two opinion polls showed Macron winning what is widely seen as France's most important election in decades with between 59 and 61 per cent of the vote.

On offer is a choice between his vision of closer integration with a modernised European Union and her calls to cut immigration and take the country out of the euro.