In Cuba, Raul Castro, the country's president, waved from a podium overlooking Revolution Square in the capital as the flag-waving crowd moved past.
Castro did not speak, leaving that task to Salvador Valdes Mesa Cuban, a labour leader and high-ranking Communist Party official .
Valdes spoke about Cuba's economic woes, saying three hurricanes last year and an ongoing global financial crisis had inflicted much damage.
Workers, he said, needed to work to raise "production and productivity, for the reduction of costs and expenditures, to grow exports and [reduce] imports".
Fidel Castro, who led Cuba for 49 years before ceding power last year to his younger brother, was not present, missing his third straight May 1 parade.
Twenty people were injured and five arrested after police clashed with demonstrators at a rally in the city of Linz, in north Austria.
In Berlin, demonstrators hurled bottles and rocks at police on Friday, injuring a number of officers, while clashes were also reported in Hamburg.
The protests were fuelled by the worsening financial crisis, especially in Germany, where the economy is expected to shrink by six per cent this year.
"No one could have imagined that this crisis could have been so profound," Michael Sommer, head of the DGB trade union federation, told a crowd in Berlin.
"There is no light at the end of the tunnel."
About 5,000 officers were on standby in the German capital, where counter-demonstrations were also expected to cause havoc.
Clashes between police and demonstrators were taking place in the Turkish city of Istanbul, with hundreds of protesters battling riot police in the streets.
|Thousands of protesters have taken to the streets in cities across France [AFP]
Security forces fired water cannons and arrested several protesters, largely made up of union and left-wing activists.
The violence has overshadowed the landmark return of annual labour rallies to the city's central Taksim Square, where on May 1, 1977, suspected rightwing snipers killed 34 people.
Anita McNaught, Al Jazeera's correspondent reporting from Istanbul, said the square had "become a lightning conductor for protests because of previous crackdowns and because of the events of 1977".
"Today, the decision has been made to allow a limited number of protesters to come right to Taksim Square to commemorate workers' day but also to commemorate the people who died in 1977.
"This is a test of crowd control on the part of the Turkish authorities but also a test of restraint on the part of the demonstrators."
Call for communism
In Greece, police fired tear gas at demonstrators who burned a car in Athens, while other activists attacked banks and traffic cameras.
Thousands of protesters in Moscow called for a return of communism, waving banners and red Soviet flags.
Far-right protests also took place in Russia, with police arresting members of anti-immigration groups in St Petersburg.
Tens of thousands of activists took to the streets across France in protest against their government's handling of the economic crisis.
France's eight main trade unions had agreed to hold united rallies across the country for the first time since the end of World War II.
Leaders of Italy's main unions held a rally in the earthquake-hit town of L'Aquila, in a show of solidarity.