Trains and ferries were cancelled and hospital staff walked off the job in Greece on Wednesday and thousands were due to demonstrate across Spain as May Day triggered protests against harsh government spending cuts.
Separately, Turkish riot police fired water cannon and tear gas to disperse crowds gathering in central Istanbul for a rally on what has become a traditional labour holiday.
In Spain, where the unemployment rate stands at a record 27 percent, the two largest trade unions, CCOO and UGT, called on workers and the unemployed to join over 80 demonstrations across the country.
In a column in financial newspaper El Economista, CCOO Secretary General Igancio Fernandez Toxo criticised the government's "huge irresponsibility" in allowing unemployment to rise to such levels.
Candido Mendez, head of UGT, said having more than 6 million people unemployed meant there had "never been a May 1 with more reason to take to the streets".
In Athens, about 1,000 policemen were deployed to handle any violence during rallies and strikes called by public and private sector unions.
It is the latest in a long line of strikes and protests in the debt-laden country ravaged by its sixth year of recession and popular fury over wage and spending cuts.
"Our message today is very clear: Enough with these policies which hurt people and make the poor poorer," Ilias Iliopoulos, general secretary of public sector union ADEDY, told Reuters.
"The government must take back the austerity measures, people can't take it anymore."
Participation, however, was expected to be well below the levels of major protests last year when as many as 100,000 Greeks marched to the central Syntagma square chanting slogans.
Unions themselves expected turnout to be low in Greece with the traditional May 1 holiday falling just a few days before Greek Orthodox Easter, which meant public schools were shut and many workers had already left for vacation.
Public transport in Athens was disrupted with buses and subways halted, while ships and ferries stayed docked at ports after seamen also walked off the job. Bank and hospital workers also joined the one-day strike.
Greek Prime Minister Antonis Samaras has sought to maintain a hard line against striking workers in a bid to show European Union and International Monetary Fund lenders - as well as the public - that he is determined to push through unpopular reforms.
In Istanbul, thousands of police were stationed across the city centre to block access to the main Taksim square as crowds of protesters converged in different parts of the city early in the morning attempting to storm police barricades.
The incidents followed the pattern of recent years, when May Day demonstrations in Turkey's largest city have often been marked by clashes between police and protesters.
Authorities often use force to prevent the rally happening in the centre of the city, having this year already denied large trade unions permission to march on Taksim, saying major construction work there would make it too dangerous.
Two officers were wounded by stones and metal objects thrown at police lines, state-run TRT television said, citing the Istanbul governor's office.
In Russia, around 1.5 million Russians were expected to participate in May 1 parades - a fraction of the millions that used to march in the Soviet times.