Hundreds of thousands of people protested across France on Thursday over President Emmanuel Macron's planned austerity policies, disrupting much of the country's public life.

Heeding a call from trade unions, protesters staged a day of actions that saw public transport stalled, schools closed and people taking to the streets for demonstrations marked by sporadic clashes with the police.

One trade union, the leftist CGT, said that more than a million people across the country had taken part in the demonstrations – higher than the 900,000 it says turned out for a June 2023 protest against the lifting of the retirement age to 64 from 62.

French authorities, whose counts are usually substantially lower than those of unions, said more than 500,000 people had demonstrated in the country, including 55,000 in Paris.

Interior Minister Bruno Retailleau said 309 people had been detained during the protests, with an alleged 7,300 "radicalised" protestors joining the demonstrations.

He added that 26 officers had been injured.

Prime Minister Sebastien Lecornu, Macron's seventh head of government since 2017, vowed a break from the past in a bid to defuse a deepening political crisis after taking office last week.

But the appointment of the 39-year-old former defence minister and close Macron ally has failed to calm the anger of unions and many French people.

"I reiterate my commitment to pursue a dialogue with all social partners" Lecornu said in a statement on Thursday, adding that he would meet again soon with union leaders.

But many protesters took direct aim at Macron, who has just 18 months left in power and is enduring his worst-ever popularity levels.

Several placards urged him to resign, and demonstrators in the southern city of Nice threw an effigy of Macron into the air.

Many complained about a growing gap between ordinary people and elites, saying a series of austerity measures proposed by the government would hit the poorest hardest.

Protesters remain incensed about the draft budget of Lecornu's predecessor Francois Bayrou, who had proposed a series of measures he said would save 44 billion euros to curb France's high debt.

Lecornu has tried to calm anger by promising to abolish life-long privileges for former prime ministers and halt a widely detested plan to scrap two public holidays.

More than 80,000 police officers were deployed, backed by drones, armoured vehicles and water cannon.

With unions calling for strikes, around one in six teachers at primary and secondary schools walked out, while nine out of 10 pharmacies were shuttered.

Commuters faced severe disruption on the Paris Metro, where only the three driver-less automated lines were working normally.

Trade unions said they were pleased with the scale of the protests. (AFP)