Protesters pelted police with missiles and were sprayed with tear gas by riot officers as May Day marches in France descended into violence.
In Paris, at least 34 people were arrested amid running battles in the streets of the French capital before the delayed march, attended by about 25,000 demonstrators, had even started on Saturday.
Local officials in Lyon said 27 police officers were injured during violence there.
Footage showed protesters launching glass bottles and other objects at officers clad in riot gear, including helmets and gas masks, and one spraying baton-wielding officers with a police tear gas cannister he had somehow obtained.
In other videos, a police officer is floored from behind and helped by colleagues as he lay injured on a pavement, and protesters are sprayed with tear gas during clashes.
In the UK, thousands of people turned out for Kill the Bill protests in cities across the country.
About 300 May Day rallies were organised in France in cities including Paris, Lyon, Nantes, Lille and Toulouse despite coronavirus lockdown rules.
In Paris, hooded, black-clad demonstrators clashed with police in Paris as an estimated 25,000 people joined the traditional May 1 protests to demand social and economic justice and voice their opposition to government plans to change unemployment benefits.
Some carried signs demanding an end to night-time curfews that were imposed as part of coronavirus lockdowns.
A number of police officers were seen with injuries during the chaos.
Police made 34 arrests in the capital, where rubbish bins were set on fire and the windows of a bank branch were smashed, momentarily delaying the march.
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Trade unionists were joined by members of the “Yellow Vest” movement, which triggered a wave of anti-government protests three years ago, and by workers from sectors hit hard by pandemic restrictions such as culture.
Marchers, most wearing masks in line with coronavirus rules, carried banners reading, “Dividends, not unemployment benefits are the income of lazy people,” and, “We want to live, not survive”.
The Prefecture de Police, which deployed 5,000 officers in Paris, said it had prevented ‘Black Bloc’ anarchists from forming a group.
“Loads of money is going to those who have plenty and less for those who have nothing as reflected in the unemployment insurance reform plan that we want scrapped,” Philippe Martinez, head of the CGT labour union said.
The union said about 150,000 people were taking part in demonstrations across France.
In Lyon, local officials said 27 police officers and gendarmes were injured during clashes.
At least five people were arrested in the south-eastern city.
Patricia, a pensioner taking part in the Lyon demonstration, told AFP: “There are so many motivations for a revolt that are building up – the management of Covid, the so-called reforms that are going to take away people’s ability to live, jobseekers who are going to lose their benefits.
“We absolutely need to express ourselves.”
Far-left leader Jean-Luc Melenchon and far-right leader Marine Le Pen, who both plan to challenge President Emmanuel Macron in next year’s presidential election, attended May Day events.
“My wish for the working class is that it can be free of the fear of being unemployed,” Melenchon told a march in Lille, adding he hoped to return to the northern city as president.
Le Pen, who had earlier laid a wreath in Paris at the statue of Joan of Arc, her party’s nationalist symbol, warned of “total chaos” if Macron is re-elected.
Macron, the former investment banker who won the presidency in 2017 promising a new way of doing politics, has seen his reform agenda become bogged down in fights with unions, while the pandemic has halted his planned pension system overhaul.
France, which has the world’s eighth-highest tally of coronavirus deaths, will start unwinding its third pandemic lockdown restrictions from Monday after a fall in infection rates.
Meanwhile, thousands of people gathered in central London to demonstrate against a proposed bill which will hand greater power to police to shut down protests deemed overly noisy or disruptive.
It was the latest in a series of protests against the Police, Crime, Sentencing and Courts Bill.
Thousands of protesters congregated around Trafalgar Square and the Mall for the “Kill the Bill” demonstration from midday on Saturday.
Later in the afternoon, the demonstrators headed towards the Home Office.
Similar protests were staged in Sheffield, Manchester and Newcastle.
In Newcastle, demonstrators faced off against officers who blocked them from accessing a police station.
One witness said: “Police closed the road and stopped access, there were a couple of scuffles and a few protestors were detained.
“After 30 minutes or so the protestors seemed to realise they wouldn’t get through so moved on.”
In Sheffield, demonstrators took the knee and gave the black power salute in a park close to the city centre, before marching towards City Hall.
Protestors in Manchester occupied Portland Street in the city centre.