France launches attempted murder investigation after petrol bomb thrown at police

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."