Thousands of Greek workers have staged a 24-hour strike, in protest against the government's austerity measures, bringing much of the country to a standstill.
The strike shut down public services and disrupted transportation on Tuesday as public and private-sector employees prepared to march in Athens, the capital, at around 0900 GMT.
Nearly 100 domestic flights have been cancelled, although international flights will not be affected, and train services were severely reduced.
Workers are protesting against the government's austerity measures, which include a radical pension reform, aimed to help the country solve its huge debt and budget deficit crisis.
Local media, schools, banks and municipal offices also shut down in the action - the fifth walkout by major public and private sector unions this year.
Tuesday's strike has also left hospitals with only emergency staff.
But authorities took swift action to stop the city's main port of Piraeus from being blockaded, where hundreds of Communist-affiliated strikers had gathered at the harbour in an attempt to stop tourists boarding ships bound for the Greek islands.
The recurring labour unrest has cost Greece booking cancellations and millions of euros in damages at a time when the debt-hit nation is struggling to maximise its revenues and revive its economy.
"Greek islanders are counting on the next month for funds," Manolis Galanakis, deputy chairman of Greek coastal shipping associations, told Mega television.
Barnaby Phillips, Al Jazeera's correspondent in Athens, said tear gas had been dispersed to dispel crowds at the port.
"There were some quite dramatic scenes this morning with tear gas being fired by the police, dispersing trade unions, many tourists running away very frightened," he said.
"Precisely not the kind of images Greece needs and it tries to get the tourist industry reinvigorated, after it got off to a slow start after all the trouble throughout the spring."
The action comes as parliament starts to discuss reforms that would raise the retirement age, cut employee benefits and curtail early pensions in an effort to bring economic recovery.
But many Greeks do not believe the financial measures will yield a positive outcome.
"These measures will not help. They will only lead to deeper recession and poverty," Despina Spanou, board member of the public sector union ADEDY, said.
"Workers will clearly answer the government and this reform which abolishes social security," Spanou said.
However, the government insists the spending cuts are vital.
"We deeply believe what we are doing is in the interests of the Greek people," George Petalotis, a government spokesman, said.
The southern European country avoided bankruptcy last month after receiving the first instalment payment of a $136bn emergency loan package from the European Union and the International Monetary Fund.
In return, Athens has passed severe austerity measures, cutting pensions and salaries and raising consumer taxes.