Polls have opened in Greece for an election expected to bring in a government led by the leftwing party Syriza, which has pledged to take on international lenders and roll back painful austerity measures imposed during years of economic crisis.

Barring a huge upset, victory for Syriza, which has led opinion polls for months, would produce the first euro zone government openly committed to writing off debt and renegotiating its EU-backed bailout deal.

Combined with last week's announcement by the European Central Bank of a massive injection of cash into the bloc's flagging economy, it would represent a turning point for Europe after years trying to fight the slump by clamping down on budgets and pushing countries to pass structural reforms.

9.8 million Greeks are eligible to vote at almost 20,000 polling stations in schools around the country, and a big turn out is expected in what is being seen as a make or break election for Greece.