Leftist SYRIZA party, which wants to revoke Greece's bailout program, is poised to win Sunday's snap poll in the country, according to exit polls.

Though polling stations are to close within a few hours, some pollsters have already announced partial results.

Figures suggest the party has a 12.5-percent lead on its main opponent, governing New Democracy.

SYRIZA's support is estimated between 35.5 and 39.5 percent, while that for New Democracy ranges between 23 and 27 percent.

This means Tsipras's party could get between 146 and 158 MP seats, with 151 needed for absolute majority that would allow him to make a government on his own. Greece's electoral system, which contains both majority and proportional elements, gives additional 50 seats to the election winner.

A Greek TV station, ANT1, reported briefly after the figure was unveiled that SYRIZA was "very close" to forming its own government.

The final opinion polls on Friday evening had predicted SYRIZA would be the winner, but will fail to attain majority in Parliament. 

Exit polls cited by the Greek Reporter suggest far-right Golden Dawn and centrist To Potami are contending for the third place at 6.4-8 percent. As of 20:00 EET (18:00 GMT) the two parties are nearly tied.

The Greek Communist party (KKE) is likely to be next, with 4.7-5.7 percent.

In what some experts would describe as "surprising" if confirmed, PASOK, the center-left party which is currently a junior coalition partner in the government, seems to have passed the threshold of 3 %, having mustered about 4.2-5.2%.

Independent Greeks, an anti-austerity party, are also almost certain to make it into Parliament with 3.5-4.5 percent of the ballots cast for them.

According to the exit polls, it is still unclear whether former PM George Papandreou's Movement of Democratic Socialists is to pass the threshold, with support ranging between 2.2 and 3.2 percent.

If the results are confirmed, the Greek vote could bring to power the first radical leftist government in Europe's recent history.

New Democracy's leader, PM Antonis Samaras, had pledged to ensure stability and progress in the debt-ridden, austerity-hit country which saw its economy contract by a quarter in six years.

Tsipras, on the other hand, had promised to end "humiliation" for Greece and not to obey "orders from abroad."

His comments earlier triggered speculation as to whether the country would remain in the Eurozone, with German weekly Der Spiegel running a story alleging that Chancellor Angela Merkel would not insist on keeping Greece inside the single-currency area.

More to follow.