Paris - French police on Monday arrested a former professional boxer seen punching officers during a "yellow vest" demonstration in Paris, as the government prepared to announce a new tough line on violent protests.
In shocking images filmed on Saturday, a heavily built man in a black duffel coat can be seen squaring up to several police officers before knocking them down in a hail of punches and then kicking them on the ground.
One of the officers is then beaten by other protesters wearing yellow vests before being rescued by fellow riot police in protective equipment and helmets.
The ex-boxer, identified by French media as 37-year-old Christophe Dettinger, is a former heavyweight fighter who reportedly works for the local government in the Essonne area south of Paris.
Interior Minister Christophe Castaner said Dettinger, known in the ring as "The Gypsy From Massy", a town south of Paris, had handed himself into police in the capital on Monday morning.
"He was immediately arrested and will be held accountable for his acts by the justice system," Castaner added.
Around 50,000 "yellow vest" protesters took to the streets again on Saturday in cities around France to denounce the centrist government of President Emmanuel Macron, leading to clashes in Paris, Bordeaux and Rouen.
Several men driving a forklift truck also smashed open the doors to the ministry building of government spokesman Benjamin Griveaux in Paris, who denounced the break-in as an "unacceptable attack on the Republic".
While the number of protesters has dwindled since December, the determination of a smaller but increasingly radical core of "yellow vest" protesters poses a dilemma for the government.
Prime Minister Edouard Philippe is set to announce new measures to tackle the unrest in a prime-time interview on TF1 channel later Monday.
Budget Minister Gerald Darmanin sought to distinguish genuine protesters, who want lower taxes and more help for low-income families, from those "who are in the business of ultra-violence".
"And faced with ultra-violence, we need to be ultra-severe. It needs to end," he told RTL radio on Monday.
French police signalled a stricter approach last week when they arrested one of the leaders of the "yellow vests", truck driver Eric Drouet, for failing to notify authorities about a demonstration.
The move led to criticism from political leaders on the far right and radical left, who have encouraged demonstrators to continue taking to the streets.
Images of a policeman striking several protesters in the southern city of Toulon on Saturday also risk fanning the flames.
The police officer -- a commander who was granted France's highest award, the Legion d'Honneur, on January 1 -- was referred to investigators at the weekend after appearing to punch a protester in the face several times.
The "yellow vest" demonstrations have frequently turned violent since they began in late November, particularly on December 1 when crowds ransacked a museum in the Arc de Triomphe and daubed graffiti on the famed monument.
The protesters drew support from a unlikely source on Monday when the two leading figures of the populist government in Rome urged the "yellow vests" to continue, in comments which risk ramping up Italy's war of words with Macron.
"Yellow vests, do not weaken!" Deputy Prime Minister Luigi Di Maio, who heads the anti-establishment Five Star Movement (M5S), wrote on his party's blog.
It is extremely rare for European leaders to back anti-government protesters in a fellow country.
The move underscored the increasingly sour relations between Rome and Paris, which have previously clashed over immigration policy, among other issues.
Dettinger, the boxer, could face years in jail if convicted over his rampage on Saturday on the Leopold-Sedar-Senghor bridge which links the Tuileries gardens to the Musee d'Orsay in central Paris.
Assaulting a police officer can lead to up to three years in prison and a fine of €45,000, though sentences can be increased in some circumstances.
The French boxing federation issued a statement condemning the violence, saying that it "ran completely contrary to the values of our sport".
Dettinger posted a video on YouTube on Sunday in which he said he had supported the "yellow vests" since the beginning and denounced "repression" from the French police.
"I was tear gassed with my friend, my wife. Anger rose up in me and, yes, I reacted badly. I defended myself," he said.
The protests against fuel taxes began in rural and small-town France against the policies and governing style of 41-year-old Macron.