French prosecutors have opened an attempted murder investigation after police were targeted with petrol bombs during unrest, according to French media. A photograph showing a police officer's leg burning during clashes in Paris on Saturday has drawn outrage after weeks of demonstrations in which protesters have also suffered injuries.

The officer sustained burns around his ankle and minor hand injuries. In an interview with Le Figaro, he described the device as “particularly sophisticated” and said investigators had not yet established what liquid it contained. According to his account, it burned with substantially greater intensity than a conventional Molotov cocktail.

Interior Minister Laurent Nuñez described the throwing of a Molotov cocktail towards a line of police as an attempted murder and said officers were seeking those responsible. Police said nobody had been arrested in connection with the filmed attack that set the officer alight, AFP reported.

Hundreds of thousands of demonstrators joined mostly peaceful rallies throughout France on Saturday. The protests were the latest in a movement led by young people that started in late September, calling for measures to address high living costs and shortcomings in public services, particularly schools.

Authorities deployed thousands of officers nationwide over the weekend after earlier demonstrations involved clashes and looting. Police used tear gas against demonstrators in some cities. The interior ministry reported more than 770 arrests on Saturday, a total approximately half that recorded during the previous week's protests.

The injured officer belongs to the National Gendarmerie, a national policing force with military status that operates under the interior ministry's control. He told Le Figaro that his unit had abruptly encountered several hundred hostile and well-equipped people. He characterised those involved as individuals seeking to hurt representatives of the state rather than protesters.

He said another 14 officers suffered injuries of varying severity, with paving stones striking some of them. His unit had been scheduled for leave but was called back urgently to help police the weekend demonstrations, he added.

The Gilets Jaunes, or Yellow Vests, who organise protests in France, say dozens of demonstrators have been seriously hurt at recent rallies around the country, many by grenades. France halted the use of one stun grenade model during student protests in early October after a 15-year-old lost a hand. Le Monde has reported that officers subsequently continued using another model.

Germany and Italy also saw demonstrations over the weekend. The protests across parts of Europe have largely been led by young people, with demands differing between movements but broadly centred on living costs and public services.