Anti-austerity Syriza looks set to take the reins of a battered Greece

Greece's Syriza party looks set for a comfortable victory over the ruling conservatives, exit polls and preliminary results from the government showed, with the anti-austerity political upstart receiving strong backing from voters angry at the spending restrictions imposed on the country by the European Union and the IMF so that Greece can pay back its international creditors.

The result is likely to trigger a standoff with austerity-minded Germany and could threaten the distribution of the next tranche of more than 7 billion euros in outstanding international aid Greece needs in the next few months.

Syriza could gain 35.5-39.5 percent of the vote, well ahead of the conservative New Democracy party of outgoing Prime Minister Antonis Samaras on 23-27 percent, according a joint exit poll for Greek television stations issued immediately after voting ended. Other individual exit polls showed similarly strong leads for Syriza, which also indicated a change that Syriza could claim an outright majority in parliament.

The first official results were released at 9:30 local time. With 27 percent of the votes counted, Syriza had won 35.44 percent, with New Democracy trailing in second with 28.8 percent. The neo-Nazi Golden Dawn was in third with 6.7 percent of the vote.

Unless the polls are badly wrong and later-counted precincts sharply reverse Syriza's gains, the vote should see 40-year-old Syriza leader Alexis Tsipras installed as prime minister and become the first head of a euro zone government to openly oppose the bailout conditions imposed by European Union and International Monetary Fund during the region's debt crisis.

With flag-waving supporters hitting the streets of Athens, some shedding tears of joy, Germany's Bundesbank warned Greece it needed to pass new laws to tackle its economic problems.

A majority?

The poll showed Syriza could have between 146-158 seats in the 300-seat parliament, with the final result heavily dependent on whether former Prime Minister George Papandreou's centre-left Movement of Democratic Socialists enters parliament.

"It is a historic victory, we still have to see if it will be a big historic victory," Syriza spokesman Panos Skourletis told Greece's Mega TV. "It sends a message against austerity and in favor of dignity and democracy," he said.

Investors have been worried a Syriza victory will trigger a new financial crisis in Greece, but the repercussions for the euro zone are expected to be far smaller than feared the last time Greeks went to the polls in 2012.

A final result could come in the early hours of Monday but after one of the shortest campaigns in recent Greek history, voters appear to have rejected the austerity medicine prescribed during a crisis which has threatened almost 4 million Greeks or a quarter of the population with poverty.

As the biggest party in the 300-seat parliament, Syriza would gain an automatic premium of 50 seats but under Greece's complicated election rules, the number of votes it needs for an absolute majority depends on how the overall vote is split up.

If he ends up short of an absolute majority, Tsipras will have to try to form a coalition with smaller parties or reach an agreement that would allow Syriza to form a minority government with ad-hoc support from others in parliament.

"The big gap between Syriza and New Democracy was a surprise because it exceeded any forecasts of a single-digit percentage gap," said Dimitris Mardas, Professor at University of Macedonia, adding they would probably still need a partner to govern.

Eyes on Berlin

Tsipras has promised to keep Greece in the euro and has toned down some of the fiery rhetoric he exhibited during his rise to prominence. But his arrival in power would herald a challenge to the approach adopted to the crisis by the wealthier euro zone governments.

Coming after the European Central Bank's move to pump billions into the bloc's flagging economy, the results will stir consternation in Berlin, which insists the bailout deal must be respected.

Asked about the reminder of the need for a change in economic management from Bundesbank President Jens Weidmann, Skourletis told Greek television: "It confirms the negotiations have already started."

Tsipras has promised to renegotiate a deal with the European Commission, European Central Bank and International Monetary Fund to write off much of Greece's 320 billion-euro debt, which at more than 175 percent of gross domestic product, is the world's second highest after Japan.

At the same time, he wants to roll back many of the austerity measures demanded by that "troika." Tsipras wants to raise the minimum wage, lower power prices for poor families, cut property taxes and reverse pension and public sector pay cuts.

Syriza officials have said they would seek a six-month "truce" to put the bailout program, due to end on Feb. 28, on hold while talks with creditors begin.

Greece, unable to borrow because of sky-high interest rates, has enough cash to meet its immediate needs but faces around 10 billion euros of debt repayments over the summer.

Without fresh cash, it will be unable to meet the payments, raising the chance of an exit from the euro.

(Additional reporting by Renee Maltezou, George Georgiopoulos, Lefteris Papadimas and Lefteris Karayannopoulos; Editing by Philippa Fletcher)