Thousands of Greeks on Thursday demonstrated against a controversial new labour law, police said, as strikes crippled transport and public services.
Some 6,000 people marched in separate protests in Athens, a police source said. Demonstrations are also held in other major cities.
The strike wave -- the second this week after a nationwide walkout on Tuesday -- shut down the civil service, sidelined ferries and halted most public transport in Athens except buses.
Several flights are also being cancelled or rescheduled owing to a work stoppage by air controllers.
According to the government, the reform introduces optional working hour flexibility, sets rules on remote work and includes safeguards against workplace sex harassment.
Government spokeswoman Aristotelia Peloni on Wednesday said the overhaul "updates legislation to the present century, to the real needs of employees today."
Labour Minister Costis Hatzidakis has said the new rules allow staff to negotiate with management the option of working more hours during part of the year, and subsequently take more time off.
But opposition parties have labelled the reform a "painful backtracking" on labour rights -- and critics say it formalises overtime exploitation by unscrupulous business owners which has already been going on for years.
-Unpaid overtime is a core problem in the Greek labour market..(and) labour inspection mechanisms have been dismantled- Nassos Iliopoulos, spokesman for the main opposition Syriza party, told Skai TV.
He also noted that under the new system, workers would negotiate without collective bargaining and would therefore be at the mercy of employers.
-This is a proposal for poorly-paid, flexible labour, a proposal from the past- Iliopoulos said.
Unions also oppose planned changes to how strikes are decided, with the government seeking to allow their members to vote remotely.
Greece in 2018 exited from a disastrous decade of debt crisis, international bailouts, tax hikes and spending cuts that wiped out thousands of jobs and created an exodus by many of the country's best-educated professionals.