France launches attempted murder investigation after petrol bomb thrown at police

Prosecutors in France have launched an attempted murder investigation after petrol bombs were thrown at police during unrest, French media reported.

An image of a police officer with his leg on fire during a clash with protesters in Paris on Saturday has prompted outrage and follows weeks of street protests in France that have also seen demonstrators injured.

The officer, who suffered burns to his ankle and minor injures to his hand, told French newspaper Le Figaro it was a "particularly sophisticated" incendiary device.

Interior Minister Laurent Nuñez said throwing a molotov cocktail at a police line was "what I call a murder attempt", adding officers were working to find the perpetrators.

Hundreds of thousands of people demonstrated across France in largely peaceful protests on Saturday, the latest in a series of youth-led protests that began in late September demanding action on the high cost of living and poor public services, especially schools.

Following previous clashes and looting, thousands of police officers were deployed across the country over the weekend, and officers fired tear gas at demonstrators in some cities.

There were more than 770 arrests on Saturday, roughly half as many as the previous week's protests, the French interior ministry said.

But police said no one had been arrested for the attack caught on camera that set a police officer on fire, AFP reported.

The officer - part of the National Gendarmerie, a national law enforcement force that is technically part of the military but under the control of the interior ministry - said his unit "suddenly found ourselves facing several hundred hostile, well equipped adversaries".

Speaking to French newspaper Le Figaro, he said police were yet to identify the liquid used but that the incendiary device "had a far greater burning capacity than a standard Molotov cocktail".

"We faced hostile individuals who are not protesters," he said. "These adversaries are there with the intent to harm those who represent the state."

Fourteen other officers sustained wounds ranging from minor to serious, he said, adding some were struck by paving stones. The unit was supposed to be on leave but had been urgently recalled to police the weekend protests, he said.

French protest organisers, the Gilets Jaunes, or Yellow Vests, have said dozens of protesters have been seriously injured during recent demonstrations across the country, with many hurt by "grenades".

France suspended the use of one type of stun grenade while policing student protests in early October after a 15-year-old's hand was blown off, but French newspaper Le Monde has reported that police have continued to use a different model in subsequent protests.

Protests also took place in Germany and Italy over the weekend, as mainly youth-led protests continue across parts of Europe, with varying demands but broadly linked to a focus on cost-of-living issues and public services.