Greek Prime Minister Alexis Tsipras has conceded defeat in the country's general election, as conservative opposition leader Kyriakos Mitsotakis secured a comfortable parliamentary majority.

With more than 90% of votes counted, Mr Mitsotakis' New Democracy party had 39.8% of the vote compared to 31.5% by Mr Tsipras' Syriza party.

In a speech from central Athens on Sunday night, Mr Tsipras said: "The citizens have made their choice. We fully respect the popular vote."

It is Greece's first parliamentary election since emerging from three successive international bailouts as it continues to struggle with a crippling nearly decade-long financial crisis.

Opinion polls had suggested Greeks were set to defy the recent European trend of increasing support for populist parties, with Mr Mitsotakis the clear favourite to win.

His centre-right party also won in the European elections in May, promising austerity-worn Greeks tax relief, stronger growth and a pro-investments stance.

In his victory speech, Mr Mitsotakis said: "From today, a difficult but beautiful fight begins."

Greek opposition New Democracy conservative party leader Kyriakos Mitsotakis talks to his supporters after a win in parliamentary elections in Athens | Image: Petros Giannakouris/AP/Press Association Images

Mr Tsipras has clashed with the country's official lenders and brought Greece to the brink of a Euro exit in his fight to undo austerity.

Greece is gradually emerging from its financial crisis that saw unemployment and poverty levels skyrocket, and the country's economy slashed by a quarter.

It was dependent for survival until last summer on international bailouts, and had to impose deep reforms - including massive spending cuts and tax hikes, to qualify for the rescue loans.

Mr Tsipras led his Syriza party to power in 2015 on promises to repeal the austerity measures of Greece's first two bailouts.

But after months of tumultuous negotiations with international creditors that saw Greece nearly crash out of the European Union's joint currency, he was forced to change tack, signing up to a third bailout and imposing the accompanying spending cuts and tax hikes.

Politicians had urged voters to cast their ballots in Sunday's general election amid fears there could be a high number of abstentions.

Many Greeks have already begun their summer holidays and there are no provisions for postal ballots.

The last time an election was held deep in the summer was 1928.