Dozens of demonstrators blocked the entrance to Greece's privatization agency offices in central Athens on Friday and planned more protests during the day against the sale of the country's two biggest ports.
Privatizations have been a key plank of Greece's succession of bailouts since 2010 but have reaped poor revenues due to political resistance, union protests and bureaucracy.
Greece has agreed the sale of a 67 percent stake in Piraeus Port to COSCO for 368.5 million euros. Under its third international bailout, Athens also plans to sell a majority stake in its second largest port in the northern Greek city of Thessaloniki later this year.
About 80 state workers and members of communist-affiliated groups rallied early in the morning outside the headquarters of the privatization agency, which manages the sales. Piraeus Port employs 1,100 people and Thessaloniki port about 400.
More protesters started rallying outside the Athens stock exchange building where Piraeus Port shareholders were expected to meet at 0800 GMT to approve the port's sale. About 300 police officers were deployed outside the building.
Last week shareholders met at a central Athens hotel to approve the sale, but the meeting was interrupted after to the protests.
Port workers have been on 48-hour rolling strikes since late May demanding that their current labor status is protected under the privatization deals, including the 36-year concession agreement with COSCO.
The strike has disrupted cargo operations and services provided to cruise ships. Cruise ship operators have warned that cruise lines will shun Piraeus for other ports if the labor action continues.