Updated

Greeks angered by a vicious and protracted financial crisis punished the parties that have dominated politics for decades Sunday, with projected election results showing them hemorrhaging support to anti-bailout groups and no party gaining enough ballots to form a government.

Responding quickly to the protest vote, the heads of the parties in first and second place pledged to seek to either renegotiate the terms of Greece's multibillion dollar international bailout agreement or overturn it.

More than two years of repeated austerity measures in return for bailout loans from other European Union countries and the IMF have pushed Greece into a deep recession that has seen the jobless rate explode and tens of thousands of businesses close. The misery has infuriated voters who on Sunday dealt a massive blow to the decades-old dominance of the country's two main parties, the socialist PASOK and conservative New Democracy.

The two, which have alternated in power since the end of the seven-year dictatorship in 1974, had managed to coexist in an uneasy alliance for the past six months as a governing coalition cobbled together to secure a second bailout deal and the biggest debt writedown in history.

Official projections Sunday showed New Democracy winning 18.9 percent, giving it 108 seats in the 300-member parliament — far short of the 151 needed to form a government. The anti-bailout left-wing Syriza party was projected second with 16.8 percent and 51 seats, and the formerly majority socialist PASOK lagged behind with 13.4 and 41 seats.

The extremist far-right Golden Dawn party, which ran on an anti-immigrant platform and wants landmines along Greece's borders, is projected to win 7 percent of the vote, giving it 22 deputies in Parliament — a massive gain for a party that until a few months ago was on the fringes of Greek politics.

With no outright majority, a coalition government will have to be formed. If successive efforts by the top three parties fail, the country will head into new elections — a prospect that has alarmed Greece's international creditors.

Both New Democracy head Antonis Samaras and PASOK leader and former finance minister Evangelos Venizelos voiced support for a coalition — but with certain caveats.

"The fact that New Democracy is the first party increases its responsibility, as it is now the only pillar of political stability in Greece," Samaras said. "We are ready to take up the responsibilty to form a new government of national salvation with two exclusive aims: For Greece to remain in the euro and to amend the terms of the loan agreements so that there is economic growth and relief for Greek society."

Before the elections, Samaras had insisted he would not form a coalition with his socialist rivals.

Syriza head Alexis Tsipras said the drubbing of New Democracy and PASOK, which had signed Greece's loan agreements, meant "their signatures have lost legal legitimacy by the popular vote."

"The people have rewarded a proposal made by us to form a government of the Left that will cancel the loan agreements and overturn the course of our people toward misery," Tsipras said.

Both statements are likely to alarm Greece's international creditors, who will be watching the debt-ridden country closely to see if it is meeting the strict fiscal targets of spending cuts and boosting revenue in return for rescue loans that are keeping it from default. The country is expected to take yet more austerity measures in June.

Partial official results with 48 percent of the vote counted showed New Democracy with 20.05 percent, Syriza with 16.02 percent and PASOK with 13.84 percent.

Golden Dawn, which rejects the neo-Nazi label and calls itself a nationalist partriotic party, had 6.86 percent — a meteoric rise for a party that won just 0.23 in the previous elections in 2009.

"Greek citizens should not fear us, the only ones who should fear us are the traitors," Golden Dawn leader Nikolaos Michaloliakos told The Associated Press.The outcome is particularly devastating to PASOK, which won a landslide victory in the last parliamentary elections in 2009 with more than 43 percent of the vote.

"For us at PASOK, the day is particularly painful," Venizelos said. "We new that we would pay the price, having taken a emotionally and politically unbearable position to take the measures that were necessary."

He ruled out a two-party government with New Democracy and called for a broad coalition of pro-European parties, regardless of their stance on the bailouts.

"A coalition government of the old two-party system would not have sufficient legitimacy or sufficient domestic and international credibility if it would gather a slim majority," Venizelos said. "A government of national unity with the participation of all the parties that favor a European course, regardless of their positions toward the loan agreements, would have meaning."

Days of talks are expected as parties attempt to hammer out a governing coalition.