A "yellow vest" protester in France had his fingers ripped off during clashes at the parliament building in Paris, as the protests went into their 13th week.
The protester attempted to pick up a rubber pellet grenade and it exploded in his hand, French media reported.
There was also an arson attack on the home of the head of France's National Assembly, though it was not clear if the attack was linked to the protests.
The "yellow vest" protests began in mid-November over fuel taxes.
They have since broadened into a revolt against the President, Emmanuel Macron, and a political class seen as out of touch with common people.
According to French government figures, 51,400 people joined the protests on Saturday, 4,000 of them in Paris. That was down from the previous week, when official figures put the number at 58,600, 10,500 in Paris.
Representatives for the yellow vests disputed the previous week's numbers, claiming the turnout was higher.
In Paris on Saturday, the protesters marched from the Champs-Elysees to the city's parliament buildings, where a violent contingent broke down barriers and threw projectiles at police. Police responded with tear gas and anti-riot munitions.
According to an eyewitness, the person who lost their hand was a photographer attempting to take pictures of people breaking down barriers around the National Assembly building.
"When the cops went to disperse people, he got hit by a sting-ball grenade in the calf," 21-year-old Cyprien Royer told AFP news agency. "He wanted to bat it away so it didn't explode by his leg and it went off when he touched it.
"We put him to one side and called the street medics. It wasn't pretty: he was screaming with pain, he had no fingers - he didn't have much above the wrist."
Paris police confirmed that a demonstrator was injured in the hand and been treated by paramedics, but did not identify the victim.
Tens of thousands of protesters turned out in other parts of France, including the port cities of Marseille and Montpellier and also in Bordeaux and Toulouse in the southwest.
Eight police officers were lightly injured during clashes with protesters in Bordeaux, local police said.
Politicians came together to condemn the arson attack on the home of Richard Ferrand, a close ally of Mr Macron, in Motreff, Brittany.
Mr Ferrand published pictures on Twitter of his scorched living room, writing: "Nothing justifies intimidations and violence towards an elected official of the Republic."