Thousands of anti-far right protesters marched across France on Saturday as opponents of presidential candidate Marine Le Pen seek to form a united front to prevent her from winning an election runoff against incumbent Emmanuel Macron on 24 April.
Police have warned of possible incidents as demonstrators convene in some 30 cities.
Macron, a pro-European Union centrist, won the presidency in 2017 after easily beating Le Pen when voters rallied behind him in the runoff to keep her far-right party out of power.
This year, the first round of voting last Sunday set up the same battle, but Macron is facing a much tougher challenge.
In central Paris, thousands of people gathered chanting anti-far right slogans and warning of democratic upheaval if Le Pen were to win. One banner read: "Against the far-right. For justice and equality, not Le Pen at the Elysee," referring to the French president's official residence.
"If the far-right is in power we will see a major collapse of the democratic, anti-racism and progressive camps," Dominique Sopo, president of SOS Racism, which along with dozens of rights groups, unions and associations called for the protests, told Reuters.
"People need to realise that despite their anger towards Emmanuel Macron and his policies, there is no equivalence between a liberal, conservative candidate and a far-right candidate."
Macron, who will hold a rally in Marseille later in the day as he tries to convince left-wing voters to pick him on 24 April, is slightly ahead in opinion polls.
But prior to the first round on 10 April Le Pen successfully tapped into anger over the cost of living and a perception that Macron is disconnected from everyday hardships. That saw her finish with 23.1% of votes compared to 27.85% for Macron.
However, she has appeared more rattled this week as the focus has turned to her manifesto and opinion polls have shown Macron extend his lead. An IPSOS-Sopra-Steria poll on Friday showed the president winning the runoff with 56% of votes.
He has won backing from former presidents Nicolas Sarkozy and Francois Hollande. Hundreds of celebrities and sporting figures have also endorsed him to block Le Pen coming to power.
Deeply undemocratic protests
Le Pen, whose stance is anti-immigration and eurosceptic, has sought in recent years to soften her image and that of her National Rally party. Opponents, including Macron, have said her programme is full of lies and false promises - an accusation Le Pen has rejected.
Speaking to reporters on a campaign stop in southern France, Le Pen dismissed the planned protests as undemocratic.
"The establishment is worried," she said. "That people are protesting against election results is deeply undemocratic. I say to all these people just go and vote. It's as simple as that."
With the electorate fragmented and undecided, the election will likely be won by the candidate who can reach beyond his or her camp to convince voters that the other option would be far worse.
For decades, a "republican front" of voters of all stripes rallying behind a mainstream candidate has helped to keep the far right out of power.
But Macron, whose sometimes abrasive style and policies that veered to the right have upset many voters, can no longer automatically count on that backing.
Highlighting how, for some voters, picking Macron is no easy decision, one banner read in Paris: "Neither Le Pen, neither Macron."
Climate change activists from Extinction Rebellion had earlier forced the closure of a main square and avenue in the capital, protesting the environmental programmes of both candidates.
"This election leaves us no choice between a far-right candidate with repugnant ideas ... and a candidate who during five years cast the ecology issue aside and lied," Lou, 26, a history teacher, who joined the Extinction Rebellion movement two years ago, told Reuters.