Alexis Tsipras has secured enough votes to give his Syriza party a "clear victory" in the country's second general election in a year and will return to power in a coalition government with the right-wing Independent Greeks.
With nearly 80 per cent of the the vote counted, the Greek Interior Ministry declared Syriza the party with the largest share of the vote:
SKAI TV reported that Tsipras' Syriza party will form a coalition government of 155 seats with its old partner, the Independent Greeks, an agreement later confirmed by Independent Greeks leader Panos Kammenos.
Speaking to crowds in central Athens after the count, Reuters reported that Tsipras said he felt vindicated, having quit and called the election last month after his party split over his own acceptance of Europe's bailout terms.
A triumphant Tsipras said that he had been given a clear, four-year mandate by the Greek people, but warned that there were difficulties ahead.
"In Europe today, Greece and the Greek people are synonymous with resistance and dignity, and this struggle will be continued together for another four years," Tspiras said, adding: "We won't recover from the struggle by magic, but it can happen with hard work."
The new coalition government will now have to lead a people who have been demoralized by austerity, a weak economy and low employment.
This disillusion was expected to be reflected in the turnout figures for the election: Around 55 percent -- a record low according to some Greece-watchers.
"While the government can most likely continue to rely on mainstream parties for support during key votes, implementing the approved measures will remain challenging," Wolfgango Piccoli of Teneo Intelligence wrote in a research note Sunday.
"Looking ahead, this situation poses the key risk for the relationship between Greece and its lenders, especially as ownership of the bailout remains non-existent: Tsipras has been rewarded for presenting himself as a critic of the bailout."
The tightly fought contest had been close to the very last polls, which suggested either New Democracy or Syriza would win the most votes by a very slim margin.
This was the Greek population's third time at the polling booth in less than a year – two elections plus the referendum on the new bailout program – and voter fatigue showed in the turnout.