Greece will work with its EU-IMF creditors for a "viable" debt deal but is determined to leave behind "disastrous austerity," Syriza leader Alexis Tsipras said after his party won the general election.
"The new Greek government will be ready to cooperate and negotiate for the first time with our peers a just, mutually beneficial and viable solution," Mr Tsipras told thousands of supporters at the party's main campaign platform in Athens.
While a final result may not come for hours, Mr Tsipras, 40, is on course to become prime minister of the first eurozone government openly opposed to the kind of austerity policies which the European Union and International Monetary Fund imposed on Greece as a condition of its bailout.
Outgoing Greek Prime Minister Antonis Samaras said he respected the decision of the Greek electorate after official projections showed voters rejecting his conservative New Democracy party in favour of the leftist Syriza party.
"The Greek people have spoken and we all respect their decision. I have a clear conscience," Mr Samaras said in a televised statement.
"New Democracy will remain ready to play a decisive role in future developments, as the guarantors of the country's European course," he said.
The party of anti-austerity leader Mr Tsipras is close to an overall majority in the 300-seat parliament, according to projections, nearly nine points ahead of New Democracy.
Mr Samaras called Mr Tsipras this evening to congratulate him on winning the election.
Antonis Samaras, outgoing prime minister, has just left the New Democracy headquarters in Athens without speaking to the media...
— Tony Connelly (@tconnellyRTE) January 25, 2015
The updated poll suggests Syriza will secure between 148 to 154 seats in the 300-seat parliament.
An absolute majority for Syriza will depend in large part on whether former Prime Minister George Papandreou's new centre-left party manages to cross the 3% threshold to enter parliament.
BREAKING: 1st official estimate puts Syriza on the edge of an overall majority with 150 seats, or 36.5pc - estimate from interior ministry
— Tony Connelly (@tconnellyRTE) January 25, 2015
Election organisers said seven parties had made it into parliament, including neo-Nazi group Golden Dawn, but it was unclear whether Syriza would secure the 151 seats necessary for an absolute majority in the 300-seat parliament.
"There is an ongoing thriller surrounding the absolute majority," said Michalis Karyotoglou, head of Singular Logic, the software group overseeing the vote process for the interior ministry.
Syriza is projected to win between 149 and 151 seats "but we might have to wait for the complete ballot count", Mr Karyotoglou said.
The prospect of a Syriza victory has worried financial markets, who fear the party's plan to demand a debt write-off and end austerity measures will trigger a new financial crisis and put Greece on the path to a euro exit.
Centrists To Potami and far-right Golden Dawn were tied for third spot with 6 to 7% of the vote, according to the exit poll.
Commenting on the outcome Irish Anti-Austerity Alliance TD Paul Murphy, who is in Greece for the election, said: "The ideological wall saying 'There Is No Alternative' to austerity has been decisively breached.
"In so doing, they have blown a breath of fresh air across Europe - giving hope in Ireland, Spain, Portugal and elsewhere that the austerity nightmare can be brought to an end."
The Greek election will increase economic uncertainty across Europe. That's why the UK must stick to our plan, delivering security at home.
— David Cameron (@David_Cameron) January 25, 2015