Trains and ferries were canceled and hospital staff walked off the job in Greece on Wednesday as workers marked May Day with a strike against harsh austerity required by the country's foreign lenders.
Elsewhere, 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 labor holiday.
Greece's 24-hour walkout was called by its two major 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."
About 1,000 policemen were deployed in central Athens to handle any violence during the rallies, though participation is 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.
Demonstrators began to slowly gather in central squares in Athens to rally before marching to parliament, the site of frequent clashes between police and protesters in recent years.
Unions expected turnout to be low 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.
The lenders' decision to disburse long-delayed aid last year has eased fears that Greece could go bankrupt and be forced to leave the euro zone, but the country still faces deep challenges from a volatile social climate and domestic opposition to a reform program that includes firing civil servants.
In Istanbul, thousands of police were stationed across the city center 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.