Greek unions staged a general strike on Wednesday and thousands of people took to the streets for May Day rallies to protest at prolonged austerity in the recession-hit nation.
Ferry services were halted to Greece's islands because of a seamen's union strike while metro and bus services in Athens were briefly halted by work stoppages.
Nearly 13,000 people joined demonstrations in Athens and the second-largest city Thessaloniki in the north, according to police estimates.
Some protesters carried flags or marched with their fists clenched in the rallies called by unions and leftist groups.
"Margaret Thatcher arrived (in Greece) with a 20-year delay," said high school teacher Katerina, referring to the late former British prime minister who was known for her hardline economic policies.
"We have lost one third of our salaries. All of us could lose our jobs at any given time," she said.
Greece, facing a sixth year of continuous recession, has one of the highest jobless rates in Europe at over 27 percent, while the figure soars to a staggering 59 percent for the under-25s.
"We only feel insecurity, there is no motive for us to study, nothing is certain," 21-year-old student Giorgos Tavoularis told AFP, fearful of the high rates of unemployment.
On Sunday, the Greek parliament voted to adopt a law that will allow the dismissal of 15,000 civil servants as part of austerity measures imposed by the indebted country's international creditors in return for desperately needed bailout funds.
The new law overturns what had been a guarantee of a job for life in Greece's notoriously bloated civil service.
"I have been unemployed ever since I got my degree two years ago," said 28-year-old archaeologist Eleni Mloukie, who has only found occasional and uninsured work as a waitress during this time.
"Being a scientist in our country means that you have no working future."
Despite the strike call, many shops remained open in Athens as the government decided to shift the May Day public holiday to May 7 because of the celebration of Orthodox Easter on May 5.
The move was an attempt by the government to help traders maximise sales during the Orthodox Holy Week.
Greece was obliged to adopt a strict austerity programme, including drastic salary and pension cuts, as part of its EU-IMF bailout deal.
Since 2010, the European Union and International Monetary Fund have committed a total of 240 billion euros ($317 billion) in rescue loans to Greece.