A voter casts ballot during the French presidential election in Paris, France, April 23, 2017. Millions of French voters began casting their ballots in the first round of the presidential election Sunday morning amid an atmosphere of uncertainty. [Photo/Xinhua]

PARIS - French voters in overseas territories started their voting for the decisive second round of presidential elections on Saturday, a day before it is scheduled in the mainland.

But the results will be only know after all votes are casted on the French mainland.

Official campaigning period ended Friday night, signalling the start of a blackout on any campaigning and media coverage, according to French electoral laws.

The polling stations in French mainland are scheduled to open at 08:00 a.m. local time (0600 GMT) and close at 20:00 p.m. (1800 GMT) in big cities, and at 19:00 (1700 GMT) in other places.

According to French law, no exit poll or early counting results of the vote is allowed to be released until all polling stations are closed.

Nearly 47 million voters are expected to cast their ballots on Sunday in 66,546 polling stations in the French mainland, where final preparation work is being carried out on Saturday.

Opinion polls indicate that pro-European Union (EU) centrist Emmanuel Macron is on course to become the country's youngest ever leader, after a tense campaign against his anti-EU challenger far-rightist Marine Le Pen.

An Ipsos-Sopra Sterna poll released on Friday showed Macron widening his lead to 63 percent of votes, up by two points compared with the previous poll, while Le Pen dropped to 37 percent.

This is Macron's best score in polls since the first round of votes on April 23.