PARIS, Sept 8, 2024 (BSS/AFP) - More than 100,000 left-wing demonstrators rallied across France on Saturday to protest against the nomination of the centre-right Michel Barnier as prime minister and denounce President Emmanuel Macron's "power grab".

The interior ministry said 110,000 people took to the streets nationwide, including 26,000 in Paris, while one leading left-winger put the turnout across France at 300,000.

Rallies took place in cities across France including Nantes in the west, Nice and Marseille in the south and Strasbourg in the east.

Macron on Thursday appointed Barnier, a 73-year-old former foreign minister who acted as the European Union's Brexit negotiator, as prime minister, seeking to move forward after snap elections in which his centrist alliance came second.

Barnier said on Friday that he was open to naming ministers of all political stripes, including "people from the left".

But a left-wing coalition, which emerged as France's largest political bloc after the June-July elections, although short of an overall majority, has denounced Macron's appointment of Barnier.

The alliance wanted Lucie Castets, a 37-year-old economist, to become prime minister, but Macron quashed that idea, arguing that she would not survive a confidence vote in the hung parliament.

On Saturday, many demonstrators directed their anger at Macron, 46, and some called on him to resign.

- 'Old elephant' -

"The Fifth Republic is collapsing," said 21-year-old protester Manon Bonijol, referring to France's current system of government.

"Expressing one's vote will be useless as long as Macron is in power," she added.

Hard-left leader Jean-Luc Melenchon, whose France Unbowed party (LFI) and allies belong to the left-wing bloc, had called for people to take to the streets, arguing that the election had been "stolen from the French".

On Saturday, he urged supporters to prepare for battle.

"There will be no pause," he vowed.

"Democracy isn't just the art of accepting that you've won, it's also the humility of accepting that you've lost," Melenchon said at the Paris march.

Project manager Alexandra Germain, 44, accused Macron of riding roughshod over the wishes of voters.

"Demonstrating is my only way of saying that I don't agree, even if I am well aware that it is useless," said Germain.

Abel Couaillier, a 20-year-old student, said he was stunned by the appointment of Barnier whom he called an "old elephant".

"I am still young, I want to believe that we can change things," added Couaillier.

Leading LFI figure Mathilde Panot claimed on X, formerly Twitter, that 160,000 demonstrators had protested in Paris and 300,000 people across France.

Police said five people had been detained in Paris.

- 'Under surveillance' -

Marine Le Pen, who leads far-right National Rally (RN) lawmakers in parliament, has said her party will not be part of the new cabinet, and that she will wait for Barnier's first policy speech in parliament before deciding whether or not to back him.

"Barnier is a prime minister under surveillance," said RN party president Jordan Bardella on Saturday.

"I am under the surveillance of all French people," said Barnier, on the sidelines of a visit to the Necker children's hospital in Paris.

Barnier will be in charge of the budget, security, immigration and healthcare.

He will have to take into account the interests of the National Rally -- the single-largest party in a fragmented legislature -- if he wants to avoid a motion of no-confidence in parliament.

Barnier -- who is likely to have only minority support in the National Assembly -- faces the urgent task of presenting the 2025 budget by early October.