Labour unions in dozens of countries around the world are using traditional May Day marches to protest over the handling of the global economic crisis, BBC reported.
In central Istanbul, Turkish police used tear gas and water cannon to disperse several hundred demonstrators.
Overnight, German youths clashed with police in the capital Berlin.
Some 300 rallies are planned across France, which has already seen strikes from university academics, hospital staff and fishermen among others.
Marches have been held in several Asian nations, including Cambodia, Japan and the Philippines.
"Workers are reiterating their demand that the government should find a way to stop mass layoffs of workers and it should provide decent jobs, not short-lived jobs, not jobs for three months," Leody de Guzman, of the Union of Filipino Workers, said.
Bottles and stones
This year's traditional Labour Day in France comes against a backdrop of mounting social tension, the BBC's Paris correspondent Emma Jane Kirby reports.
There is a growing perception that little has been done to protect the ordinary person's job and wages while executives from banks bailed out by the government have enjoyed generous pay-offs and bonuses, she says.
The country's eight main unions have urged people to come out and protest in their third such day of action this year.
Violence erupted in Istanbul as hundreds of left-wing and trade union groups tried to pass through police checkpoints into the city's main Taksim square.
The protesters had been refused permission to hold rallies in the square but, as in previous years, they chose to ignore the ban, the BBC's David O'Byrne in Istanbul reports.
The marchers took to the back streets after they were met with police water cannons, and hurled stones and other missiles at police who responded by firing tear gas.
A large number of people are believed to have been arrested and there is considerable damage to shops and vehicles, but no serious injuries, our correspondent reports.
In Berlin, demonstrators clashed with police. Bottles and stones were thrown at police, passing cars and trams, and rubbish bins were set alight.
It began when some 200 protesters began chanting anti-capitalism slogans after a street party ended in the early hours.
Twenty-nine police were injured, and at least 12 people were arrested.
Violence has been a feature of past May Days in Germany. Some 5,000 police are set to be deployed in Berlin.
Major marches are also planned in Spain, Italy, Russia and Cuba.