France's far-right party National Rally (RN) emerged ahead in the first round of parliamentary elections on Sunday, exit polls showed.
French President Emmanuel Macron called for a "broad, republican and democratic" alliance against the anti-immigration party, urging another high turnout in the second round of voting on July 7.
The RN won about 34 per cent of the vote, exit polls from Ipsos, Ifop, OpinionWay and Elabe showed.
That was ahead of leftist and centrist rivals, including Mr Macron's Together alliance, which was considered to be winning 20.5 per cent to 23 per cent.
The New Popular Front, a left-wing coalition, was projected to win about 29 per cent of the vote, the exit polls showed.
Mr Macron called a surprise ballot after his centrist alliance was crushed by Marine Le Pen’s anti-immigrant and eurosceptic RN in European elections.
"Nothing is won and the second round is decisive," Ms Le Pen told supporters after the RN came out on top in the first round of polls.
"We need an absolute majority so that Jordan Bardella is in eight days named prime minister by Emmanuel Macron."
At Ms Le Pen's Henin-Beaumont constituency in northern France, supporters waved French flags and sung the Marseillaise.
"The French have shown their willingness to turn the page on a contemptuous and corrosive power," Ms Le Pen said.
The RN's chances of winning power next week will depend on the political deal-making by its rivals over the coming days.
In the past, centre-right and centre-left parties have teamed up to keep the RN from power, but that dynamic, known as the "republican front," is less certain than ever.
If no candidate reaches 50 per cent in the first round, the top two contenders automatically qualify for the second round, as well as all those with 12.5 per cent of registered voters.
In the run-off, whoever wins the most votes take the constituency.
High turnout on Sunday suggests France is heading for a record number of three-way run-offs. These generally benefit the RN much more than two-way contests, analysts said.
Support for Mr Macron's centrist camp has collapsed in recent weeks, while left-wing parties put their disputes aside to form the New Popular Front, in a nod to an alliance founded in 1936 to combat fascism.
The polls first opened in France’s overseas territories and at 8am local time across the country, with 49 million people eligible to vote.
Casting his vote in Sevres, on the outskirts of Paris, former company director Didier Delacroix, 70, said he had voted for Mr Macron's alliance, saying “otherwise it'll be a complete mess”.
In Henin-Beaumont, Denis Ledieu, 67, said people were suffering from the long-term deindustrialisaton of the region.
"So if the [RN] promises them things, then why not? They want to try it out, I think," he said.
In the town of Meaux, Mylene Diop, 51, said she had voted for the New Popular Front, in what she said was "the most important election" of her life.
"The RN is at the gates of power and you see the aggressiveness of people and the racist speech that has been unleashed," she said.
The election is a two-stage process and the shape of the 577 seat lower house of National Assembly will only become clear after the second round of voting on July 7.
Vincent Martigny, professor of political science at the University of Nice and the Ecole Polytechnique, said this opens the door for the RN.
"If you have a very high level of participation you might have a third or fourth party that is getting into the struggle,” said Prof Martigny.
“So then of course there's a risk of split voting and we know that the split vote favours the National Rally.”
With the French facing their most polarising choices in recent history, turnout soared.
The Elabe organisation projected a final turnout of 67.5 per cent, the highest participation in a regular format legislative election in France since 1981.
The final turnout in 2022 was just 47.5 per cent.
RN party chief Mr Bardella was seen out early casting his vote in Garches, in the suburbs of Paris, with Mr Macron later voting in Le Touquet, in northern France.
Mr Bardella, 28, a protege of Ms Le Pen who has no governing experience, could become prime minister in a tense "cohabitation" with Mr Macron.
The RN was a long-time pariah but is now closer to power than it has ever been as Ms Le Pen has sought to moderate the party’s extremist image.
If elected, Mr Bardella said he will propose immediate legislation within weeks to the lower house of parliament to tackle what the party calls the “flood” of migration.
It would abolish the policy of automatically granting French nationality at 18 to people born in France to foreign parents, providing they have lived here for at least five years since the age of 11.
The RN also has plans to toughen conditions for family reunification.
Among its other policies would be giving French citizens priority access to housing and jobs, with welfare benefits limited to French nationals.
Under RN there would be strict conditions of assimilation for those seeking citizenship, including mastery of the French language and respect for French laws and customs.
Mr Bardella said some of the measures would be put to a nationwide referendum in 2027, after the presidential election that year, to sidestep challenges from the Constitutional Council.
The council has previously ruled that RN-proposed changes to French immigration laws were unconstitutional.
If the RN does win an absolute majority, French diplomacy could be heading for a period of turbulence as Mr Macron and Mr Bardella vie for the right to speak for France.
A clear RN victory would also bring uncertainty as to where France stands on the Russia-Ukraine war.
Ms Le Pen has a history of pro-Russian sentiment and while the party now says it would help Ukraine defend itself against Russian invaders, it has also set out red lines, such as refusing to provide long-range missiles.
