Greeks have begun voting in their third national polls this year, called on to choose who they trust to steer the country into its new international bailout.

Former Prime Minister Alexis Tsipras' left-wing Syriza party, which made pledges to implement austerity measures in return for billions of euros in rescue loans, was marginally ahead of the rival center-right New Democracy in opinion polls leading up to Sunday's vote. But the polls indicated the winner would not have enough votes to form a government alone.

Tsipras triggered the election by resigning barely seven months into his four-year term, after facing a rebellion within Syriza over his policy U-turn in accepting the spending cuts and tax hikes stipulated by the bailout.

Tispras had won January elections on a promise to abolish austerity.