Greece's conservative New Democracy party has admitted defeat to Alexis Tsipras's left-wing Syriza in the nation's fifth election in six years, reported the BBC Sunday.
Syriza led New Democracy by 35% to 28% with a third of votes counted, according to interior ministry data.
This is likely to leave Syriza just short of an absolute majority, and in need of coalition partners.
The snap election was called after Syriza lost its parliamentary majority in August, after the signing of an unpopular new financial bailout deal with international creditors.
New Democracy leader Vangelis Meimarakis said Sunday: "The electoral result appears to be concluding with Syriza and Mr Tsipras in the lead. I congratulate him and urge him to create the government which is needed."
Syriza supporters at the party's main electoral HQ in Athens hugged Tsipras as he arrived there.
He later said there was "hard work and struggle" ahead for the Greek people.