Prime Minister Alexis Tsipras has promised radical change as his new government swiftly moved to roll back key parts of Greece's international bailout, prompting a third day of losses on financial markets.

A swift series of announcements signalled the newly installed government would not back down from its anti-austerity pledges, setting it on course for a clash with European partners, led by Germany, which has said it will not renegotiate the aid package needed to help Greece pay its debts.

Even before the first meeting of the new cabinet, ministers had hit the airwaves to reassure voters they would honour campaign pledges to roll back the tough economic policies imposed under Greece's 240-billion-euro bailout programme.

The planned sale of a 30 per cent stake in Public Power Corporation of Greece (PPC), the country's biggest utility, was halted while ministers pledged to raise pensions for those on low incomes and reinstate some fired public sector workers.

"We are coming in to radically change the way that policies and administration are conducted in this country," Mr Tsipras told ministers at their first cabinet meeting.

Financial markets have looked on nervously, with Greek 10-year bond yields up 50 basis points at 10.30 per cent, the main Athens stock index down 4 per cent and bank stocks down 12.6 per cent to extend losses into a third day.

Saying that the mood towards Greece was changing since his left wing party's sweeping election victory on Sunday, Mr Tsipras said he would avoid antagonism with EU and International Monetary Fund creditors.

"Our priority is also a new negotiation with our partners, seeking to reach a fair, viable and mutually beneficial solution so that the country exits the vicious circle of excessive debt and recession," he said.

He said the government would pursue balanced budgets but would not seek to build up "unrealistic surpluses" to service Greece's massive public debt of more than 175 percent of gross domestic product.

He added that he expected a "productive" meeting on Friday with Jeroen Dijsselbloem, head of the eurozone finance ministers' group.