Greece ordered electricity workers back to their jobs yesterday, threatening them with arrest if they continue with strikes that have caused power cuts across the country in the middle of its tourism season.

The move came after workers at Public Power Corp (PPC), Greece's biggest power producer, defied a court ruling deeming their strike action illegal.

Protesting against government plans to sell part of PPC in 2015, workers had initiated the first of a series of 48-hour strikes at midnight on Wednesday, then started a second action at midnight Friday. Unions say the sale will push up electricity prices and impose an extra burden on households struggling through years of recession.

But the government defended its policy.

"Since day one, the government's intention was and remains to protect the public interest," government spokeswoman Sofia Voultepsi said in a statement announcing the back-to-work order. "In a democracy, the law and court rulings must be respected by everyone."

PPC's biggest trade unions was to hold a meeting later yesterday to decide how to continue their action. Communist-affiliated PAME said it planned a rally in Athens later in solidarity with the workers.

"The government cannot give away PPC ... for free," George Avramidis, head of Spartakos, one of PPC's most powerful unions in northern Greece, said.

Athens is eager to avoid major power disruption this summer as it could impact tourism, the biggest earner for the Greek economy, accounting for about 17 per cent of its output and 20 per cent of jobs.

Under Greek law, striking workers can be ordered in writing to return to work where there is a danger of civil disorder, natural disaster or health risks to the public.

Prime Minister Antonis Samaras's government last invoked the measure in 2013 to force seamen and subway workers back to their jobs after week-long walkouts.

Privatising PPC is part of efforts by Greece to liberalise its energy market at the behest of its European Union and International Monetary Fund lenders and is one of the conditions for its next aid tranche worth 1 billion euros.

The leftist main opposition Syriza party, which wants PPC to remain in state hands, has backed the workers and said it will not support the bill allowing the sale of 30 per cent of PPC to a private competitor.-Reuters