Paris (France) (AFP) - After weeks of student protests, France is set to be swept by broader, nationwide demonstrations Saturday over the cost of living, setting up a potentially fraught period ahead of presidential elections next year.

The prospect of the two movements merging, perhaps with outbreaks of violence, poses a big challenge to the government – and an opportunity for far-left and far-right presidential candidates jockeying for power.

The country’s Yellow Vest movement, which eight years ago staged street protests against President Emmanuel Macron and his government, called Saturday’s “yellow and youth” demonstrations and urged millions to turn out.

It has appealed to teachers, workers, pensioners and farmers, as well as students, in an online call spread through social media.

“We’re expecting a pretty big turnout,” Interior Minister Laurent Nunez told France 2 television.

A police source told AFP that authorities estimated nearly 200,000 people could take part, with 40,000 of them in Paris.

“I have a feeling that (Saturday) will be a sort of culmination,” 18-year-old Marie-Lou, a protesting university student in the city of Lille, told AFP.

“We’ll be joined by workers and by the Yellow Vests, who are also mobilising again. There’s a sense of hope that all these different struggles might converge.”

Prime Minister Sebastien Lecornu on Friday ordered a crisis cell be set up to monitor the demonstrations in real time. On Thursday he said he feared clashes after what he called “urban violence” during the student protests.

Lecornu is attempting to get the parliament to pass a cost-cutting budget, while protesters are demanding greater protection from inflation and more spending on public services, particularly education.

- Anger at police -

There is also public anger at perceived police brutality during the student protests, at which several teenage protesters were maimed and thousands arrested.

“It’s not just a Yellow Vest movement, it’s not just a student movement, it’s all the people who are rising up and that’s why those in power are afraid,” said Benjamin Ball, an activist working on a website for Saturday’s demonstrations.

The growing unrest is weighing on the final months of Macron’s presidency, ahead of elections in April and May to choose his successor.

It has been seized upon by opposition parties and their candidates.

Jean-Luc Melenchon, leader of the far-left France Unbowed party, has backed the student protests and marched in a demonstration Tuesday supporting them.

Far-right leader Marine Le Pen, the frontrunner according to surveys, has positioned her National Rally party on the side of the police, consistent with its law-and-order messaging.

Macron this week said he believed the “legitimate” demands of the protesting students were being “exploited for political purposes”, according to a government spokeswoman.

- Prepared for violence -

Organisers of Saturday’s demonstrations have set up a website showing more than 600 demonstrations planned across France, and hundreds more protest “actions” such as blocking motorway toll booths or service stations.

Both authorities and demonstrators were preparing for possible violence.

Paris’s police banned a major march through the tourist and business heart of the capital, and are locked in negotiations with organisers over an alternative route. The main demonstration in the capital was to kick off at 2:00 pm (1200 GMT) in the public square at Bastille.

Nunez told France 2 that officers could use stun grenades in case of “extremely serious urban violence”. He had previously suspended their use during the student protests after one stun grenade blew off the hand of a 15-year-old.

“Disturbances are expected, especially in the demonstrations in Paris and other big cities,” an interior ministry official told AFP on condition of anonymity, citing a risk of violence from “the ultra-left movement”.

“Actions blocking major roads or large, essential facilities will not be tolerated,” the official said.

Demonstrators have set up their own smartphone app giving the real-time location of police, tear gas and helicopters.