PARIS (AFP) - Riot police clashed with hooded youths on the fringe of a protest in central Paris on Tuesday (Sept 12) against French President Emmanuel Macron's reforms to loosen labour regulations.
Police fired water canons and could be seen dragging several demonstrators behind their lines, TV images showed.
Tens of thousands of French protesters marched against Mr Macron's flagship economic reforms in the first major demonstrations against his pro-business agenda.
The day of strikes and rallies are seen as a key test for the young French leader as he stakes his presidency on overhauling the sluggish economy, while protesters are eager to show they are able to mobilise in large numbers.
Some 4,000 strikes and 180 protests were called by France's biggest trade union, the CGT, with rail workers, students and civil servants urged to join the protests against proposed changes to labour law.
"It's a first one and it looks like it's a success," the head of the CGT, Mr Philippe Martinez, said at the start of a rally in Paris, claiming that 100,000 people had answered his union's call countrywide.
Police figures for the number of demonstrators are likely to be significantly lower, with turnout being scrutinised as a measure of the strength of resistance to the reforms.
As well as Paris, crowds of a few thousand people gathered in the cities of Nice, Marseille, Saint Nazaire, Toulouse and Caen.
The disruption to rail networks, air traffic control and public services appeared limited, however.
The business-friendly Mr Macron wants to make France more attractive for both French companies and foreign investors who have long complained about restrictive labour laws and the power of trade unions.
He has vowed to press ahead with the reforms, which aim to give companies more flexibility in negotiating terms and conditions with their employees while reducing the costs of firing workers.
But the 39-year-old president antagonised his opponents with outspoken comments last week when he described critics of his government's efforts as "slackers" and "cynics".
Mr Bruno Cautres of the Cevipof political research institute said the former investment banker had "added fuel to the fire" with his choice of words.
"With the 'slackers' comment, there are all the ingredients for this to heat up," he said.
Protesters seized on the remark on Tuesday, with the word daubed on banners and placards while others shouted, "Macron you're screwed, the slackers are in the street."
"I think that it led lots of people to come out today," said Mr Mehdi, a protester in Paris whose friend held a sign saying, "Come and see how the slackers work!!!"
But Mr Macron can also count on deep splits in the labour movement between the CGT and its hardline allies, which are determined to obstruct the reforms, and others prepared to compromise and negotiate.
"We need to stop thinking that trade union action only makes sense when we demonstrate," the head of the moderate CFDT, Mr Laurent Berger, told Franceinfo radio on Tuesday.
The CFDT, the largest union in the private sector, and the leader of the usually fiery Force Ouvriere (FO) union have both declined to join the strike action.
A separate protest movement on Tuesday by fairground operators swelled the numbers on the streets and their trucks, some towing merry-go-rounds on trailers, blocked roads in Paris and some regional cities.
Mr Macron is hoping to avoid a re-run of mass demonstrations against labour reforms initiated by his Socialist predecessor Francois Hollande that rocked France for months last year.
Mr Macron - whose approval ratings have slumped sharply since he came into office - was in the Caribbean on Tuesday visiting French islands hit by Hurricane Irma last week.
"What is going to be a surprise is when he ends up giving ground," hard-left leader Jean-Luc Melenchon told reporters as he joined a protest in the southern port of Marseille on Tuesday.
"This country doesn't want the liberal world... France isn't Britain," he added.
The CGT plans to follow Tuesday's actions with a second protest day on Sept 21, with another two days later called by far-left firebrand Mr Melenchon.
The centrist president, who swept to power in May on promises to reinvigorate the economy, has used executive orders to fast-track the changes.
They are to take effect later this month even before being ratified by Parliament, where Mr Macron's Republic on the Move party has a large majority.
The new law will give small company bosses in particular more freedom to negotiate working conditions directly with their employees rather than being subject to industry-wide agreements.
Compensation for unfair dismissal will be capped, a move that has particularly angered unions, along with steps to make it easier for foreign-based companies to lay off staff in struggling French operations.