A French policeman is in "very critical condition" after suffering a cardiac arrest in the middle of the 19th consecutive weekend of "gilets jaunes" (yellow vests) protests on Saturday.
Footage taken by Reuters shows emergency services trying to resuscitate the police officer.
French Interior Minister Christophe Castaner said the policeman suffered a "serious cardiac arrest" and that he was closely monitoring his condition.
Protesters marched in Paris despite new security measures rolled out in a bid to quell violence at protests.
It comes after violent scenes on a landmark Parisien boulevard last Saturday that saw demonstrators torch Le Fouquet restaurant.
The scenes of lawlessness prompted the government to act: Paris' police chief was replaced, protesters have been banned from the Champs-Élysées and fines for illegal gatherings have been increased.
This made the protests more peaceful than in previous weeks. There were only a few skirmishes on Saturday afternoon when police faced off with demonstrators that had started a fire in the 10th district.
Similar restrictions have been put in place in other French cities, such as Nice and Bordeaux, with more protests expected Saturday.
There were an estimated 40,500 demonstrators across France, with 5,000 in Paris, said Castaner.
The military has also been controversially put on standby. The government insists they are only there to protect official buildings and sensitive sites.
Bruno Retailleau, leader of Les Républicains Senators, said on Wednesday that Macron should “reverse this disastrous decision”.
Socialist Party candidate, Benoît Hamon, expressed his concerns on Thursday that the government was releasing an "arsenal of security and martial measures".
The "gilet jaunes" demonstrations began in November amid anger over rising fuel taxes, but have since snowballed into a broader backlash against France's president, Emmanuel Macron, and his government.
The protests, now into their fourth month, initially attracted more than 300,000 demonstrators, but turnout has been steadily falling.
Last Saturday there were 32,000 protesters across France, according to the authorities.