Thousands of police deployed as France braces for new wave of protests

France on Thursday ordered the mobilisation of tens of thousands of police to prevent a further escalation of violence after two nights of clashes over the killing of a teenager by a policeman.

Cars and bins were torched in parts of the country, while some 150 people were arrested nationwide following clashes and unrest that included a tramway's carriages being alight in a Paris suburb.

France has been hit by protests after Nahel M., 17, was shot Tuesday in the chest at point-blank range in the Paris suburb of Nanterre in an incident that reignited debate about police tactics.

On Thursday, a prosecutor said the policeman's use of his firearm had not been legal under the circumstances, and he would be taken before a magistrate with a view to being charged with homicide.

President Emmanuel Macron has called for calm and said the protest violence was "unjustifiable".

Macron told a crisis meeting of ministers that the coming hours and an afternoon march in memory of Nahel in Nanterre should be marked by "contemplation and respect".

Interior Minister Gerald Darmanin said a total of 40,000 police would be deployed across France on Thursday, more than four times Wednesday's numbers on the ground, with 5,000 to be sent out in Paris alone.

The riots are deeply troubling for Macron who had been looking to move past a half-year of sometimes violent protests over his controversial pension reform.

Nanterre prosecutor Pascal Prache said he was asking for the 38-year-old policeman, who was to appear before an investigating magistrate, to be remanded in custody.

The teenager was killed as he pulled away from police who tried to stop him for traffic infractions.

A video, authenticated by AFP, showed two policemen standing by the side of the stationary car, with one pointing a weapon at the driver.

A voice is heard saying: "You are going to get a bullet in the head."

The police officer then appears to fire as the car abruptly drives off.

Clashes first erupted as the video emerged to contradict police accounts that the teenager was driving at the officer.

Wednesday night anger spread to Toulouse, Dijon and Lyon, as well as several towns in the Paris region.

Overnight Wednesday to Thursday, masked demonstrators dressed in black launched fireworks at security forces near the scene of Nahel M.'s killing.

A thick column of smoke billowed above the area where a dozen cars and garbage cans were set ablaze and barriers blocked off roads.

Graffiti on the walls of one building called for "justice for Nahel" and said, "police kill".

In Paris, police fired flashballs to disperse protesters who responded by throwing bottles.

In the southern city of Toulouse, several cars were torched and police and firefighters pelted with projectiles.

At France's second-largest prison complex, Fresnes, protesters attacked security at the entrance with fireworks.

The town hall of Mons-en-Baroeul outside the northern city of Lille was set on fire when some fifty hooded people stormed the building, the mayor told AFP.

Prime Minister Elisabeth Borne, speaking in a town north of Paris where the mayor's office had been set on fire, said "obviously all escalation has to be avoided".

France is haunted by the prospect of a repeat of 2005 riots, sparked by the death of two boys of African origin in a police chase, during which 6,000 people were arrested.

"There are all the ingredients for another explosion potentially," one government adviser told AFP on condition of anonymity.

The head of the right-wing Republicans, Eric Ciotti, called for a state of emergency, which allows local authorities to create no-go areas, but a government source told AFP this option was not currently on the table.

There has been growing concern over police tactics, particularly against young men from non-white minorities.

Last year, 13 people were killed after refusing to stop for police traffic checks, with a law change in 2017 that gave officers greater powers to use their weapons now under scrutiny.

"What I see on this video is the execution by police of a 17-year-old kid, in France, in 2023, in broad daylight," said Greens party leader Marine Tondelier.