Police have fired tear gas and water cannons on crowds of yellow-vested protesters trying to march on the French presidential palace, demonstrating against high taxes and Emmanuel Macron.
Parts of central Paris are in lockdown, with huge numbers of police deployed around the capital as the country braces for outbreaks of violence after the worst rioting in Paris in decades in recent weeks.
Police and protesters also clashed in other French cities, notably Marseille, Toulouse and Bordeaux, and in neighbouring Belgium.
Some protesters took aim at the French border with Italy, creating a huge traffic backup near the town of Ventimiglia.
Across the country, more than 1,100 people were arrested.
It is estimated that 10,000 people took part in protests in Paris, among 125,000 nationwide.
At least 135 people are thought to have been injured in Paris, including 17 police officers, in violent clashes.
France's Interior Minister Christophe Castaner said the skirmishes in the capital were "under control", but branded the violence "unacceptable".
The protesters began to assemble before dawn, with demonstrators waving French flags and wearing the movement's signature high-visibility vests gathering near the Arc de Triomphe, which was damaged in last week's rioting.
Others lined up for police searches and bag checks throughout central Paris.
Rows of riot police blocked the demonstrators' passage down the Champs-Elysees toward the heart of presidential power, firing tear gas and pushing them back with shields.
A ring of steel surrounds the Elysee Palace itself as police stationed trucks and reinforced steel barriers in streets throughout the neighbourhood.
Many shops along the avenue boarded up their windows in anticipation of violence and damage, which many angry protesters attempted to rip off.
As the day wore on, protesters threw projectiles and flares, smashed windows, and set fires, but were repeatedly pushed back by the more than 8,000 police officers deployed throughout the capital.
Despite the repeated skirmishes, Saturday's anti-government protests appeared less chaotic and violent than a week ago, when crowds defaced the Arc de Triomphe, set vehicles ablaze and looted high-end stores in the city's worst rioting since 1968.
Some 130 people were injured in last week's clashes.
The Eiffel Tower and Louvre Museum are among the sites that remain closed, fearing damage after rioting and looting last Saturday that saw 130 people injured.
Ahead of Saturday's protest, Mr Macron's government warned that the "yellow vest" demonstration in Paris has created and "monster" and would be hijacked by "radicalised and rebellious" crowds and become the most dangerous yet after three weeks of demonstrations.
The demonstrations are not only confined to Paris, tens of thousands of police took position around France to face protesters angry at President Emmanuel Macron and France's high taxes.
Authorities deployed barricade-busting armoured vehicles and 8,000 police in the capital alone.
Nationwide, 89,000 security forces fanned out to deter or confront troublemakers expected at multiple protests.
The grassroots movement began as resistance against a rise in taxes for diesel and petrol, but quickly expanded to encompass frustration at stagnant incomes and the growing cost of living.
Mr Macron agreed to abandon the fuel tax hike, but that has not defused the anger, embodied by the fluorescent safety vests French motorists are required to keep in their cars.
The protesters are not unified and have many different demands, meaning that the agreement not to hike fuel taxes and a pledge not to increase energy bills has not placated everyone.
Moreover, the lack of unification means that there is no leadership to the movement, making it hard for the government to enter negotiations.
Many members of the protest movement are calling for calm, and some struck a conciliatory tone after meeting the prime minister on Friday night in a last-minute bid to cool tempers, but that did not deter many people from trying to march on the presidential palace on Saturday.
Interior minister Christophe Castaner urged calm: "I ask the yellow vests that want to bring about a peaceful message to not go with the violent people. We know that the violent people are only strong because they hide themselves within the yellow vests, which hampers the security forces."
Mr Macron himself has been largely invisible in recent days, including on Saturday, leaving his prime minister and government to try to negotiate with protesters. On Friday night he met riot police being deployed in Paris on Saturday.
A separate march for the environment has taken place peacefully in Paris and other cities in France, and attracted a more diverse crowd, with far more women and older people and a handful of children taking part.
The climate change march in Paris was bigger than the other protest, with around 17,000 people taking part.
A handful of people in yellow vests had joined the quiet march by mid-afternoon.
One sign read "No climate justice without fiscal and social justice."
Donald Trump claimed that the protesters were demonstrating over the landmark Paris Agreement on climate change, and that people were chanting "we want Trump".
Despite the US President's claims, there was no evidence to support them.
Four people have been killed in accidents since the unrest began on November 17.
Christmas markets, national football matches and countless other events have been cancelled or disrupted by the protests.
Parts of Paris looked like they were bracing for a hurricane, with boards on windows covering up the Christmas decorations.
Police removed any materials from the streets that could be used as weapons, especially at construction sites in high-risk areas.
Protesters also blocked roads, roundabouts and tollbooths elsewhere in France.
Offshoot movements have emerged elsewhere, and yellow-vest protests are planned on Saturday in Belgium and the Netherlands.