Greek prime minister Kyriakos Mitsotakis, whose conservative party has won a landslide election but without enough parliamentary seats to form a government, has said he will seek a second election to consolidate his victory without the need for a coalition partner.
Mr Mitsotakis's New Democracy party was 20 percentage points ahead of its main rival, the left-wing Syriza party, with nearly 90% of the votes counted on Sunday.
But due to the current electoral system of proportional representation, his 40% vote share was still not enough to secure a majority of the 300 seats in parliament, meaning he would either have to seek a coalition partner from a smaller party, or head to a second election.
"From tomorrow, I will follow all constitutional procedures, but maintaining my firm view that the mathematics of proportional representation is akin to party horse-trading and results in a dead-end," Mr Mitsotakis said.
"Without a doubt, the political earthquake that occurred today calls on us all to speed up the process for a definitive government solution so our country can have an experienced hand at its helm as soon as possible."
A new vote, likely in late June or early July, will be held with a new electoral law which gives bonus seats to the winning party, making it easier for it to form a government on its own.
With nearly two thirds of the vote counted, the left-wing opposition party of former PM Alexis Tsipras was trailing with 20% of the vote, compared with 40% for Mr Mitsotakis' New Democracy party.
Sunday's election was Greece's first since its economy ceased being under the strict supervision of international lenders who had provided bailout funds during the country's nearly decade-long financial crisis.
Mr Tsipras, 48, served as prime minister during some of the most tumultuous years of the crisis, and has struggled to regain the wide support he enjoyed when he was swept to power in 2015 on a promise of reversing bailout-imposed austerity measures.
He called Mr Mitsotakis on Sunday to congratulate him on his victory.
"The result is exceptionally negative for Syriza," Mr Tsipras said after his party's dramatic defeat became clear. "Fights have winners and losers."
He said his party would gather to examine the results and how they came about.
"However, the electoral cycle is not yet over," he said. "We don't have the luxury of time. We must immediately carry out all the changes that are needed so we can fight the next crucial and final electoral battle with the best terms possible."
As the massive gap between the first two parties became apparent, Syriza supporters expressed dismay.
"I am very sorry about the terrible state of these people (who voted for New Democracy)," said Syriza supporter Georgi Koulouri, standing near a Syriza campaign kiosk in central Athens.
"People who understand their position, the poverty and the misery that they have been put into, and still vote for them, they deserve what they get."
Mr Mitsotakis, 55, a Harvard-educated former banking executive, won 2019 elections on a promise of business-oriented reforms and has vowed to continue tax cuts, boost investments and bolster middle-class employment.
He had been steadily ahead in opinion polls in the run-up to the election but his popularity took a hit following a rail disaster in February that killed 57 people after an intercity passenger train was accidentally put on the same rail line as an oncoming freight train.
It was later found that train stations were poorly staffed and safety infrastructure broken and outdated.
The government was also battered by a surveillance scandal in which journalists and prominent Greek politicians discovered spyware on their phones.
Mr Mitsotakis has delivered unexpectedly high growth, a steep drop in unemployment and a country on the brink of returning to investment grade on the global bond market for the first time since it lost market access in 2010, at the start of its financial crisis.
Debts to the International Monetary Fund were paid off early.
European governments and the IMF pumped 280 billion euros (£260 billion) into the Greek economy in emergency loans between 2010 and 2018 to prevent the eurozone member from bankruptcy.
In return, they demanded punishing cost-cutting measures and reforms that saw the country's economy shrink by a quarter.