ATHENS, Greece – Furious Greeks punished the two parties that have dominated politics for decades in the crisis-battered country Sunday, leaving its multibillion-dollar bailout — and even its future in the euro currency — hanging in the balance.

With more than 83 percent of the vote counted, Greece appeared to be heading toward political stalemate. Nobody won enough votes to form a government, and the two parties that backed the bailout — the conservative New Democracy and socialist PASOK — conceded they need to win over adversaries to form a viable coalition.

“I understand the rage of the people, but our party will not leave Greece ungoverned,” said New Democracy leader Antonis Samaras.

New Democracy was leading with nearly 20 percent of the vote, which would give it 110 seats in the 300-member parliament. PASOK, which has spent 21 years in government and stormed to victory with more than 43 percent in 2009, saw its support fall to about 13.5 percent. It will have just 41 seats, compared to 160 in the last election.

The two parties saw their support plummet to the lowest level since Greece emerged from a seven-year dictatorship in 1974.

The outcome showed widespread anger at the austerity measures imposed in return for rescue loans from other European Union countries and the International Monetary Fund. Without the funds, Greece faced a default that could have dragged down other fiscally troubled European countries and seen it leave the euro.

Voters who deserted the two mainstays of Greek politics in droves headed to a cluster of smaller parties on both the left and right, including the extremist Golden Dawn, which rejects the neo-Nazi label and insists that it is nationalist and patriotic. The movement has been blamed for violent attacks on immigrants and ran on an anti-immigrant platform, vowing to “clean up” Greece and calling for land mines to be planted along the country’s borders.

The party looked set to win about 7 percent of the vote, giving it 21 deputies in parliament. The group earned just 0.29 percent of the vote in 2009.

Sunday’s other big winner was Alexis Tsipras, 38, the leader of the Radical Left Coalition, who saw his party poised for an unprecedented second place with 16.4 percent and 51 seats .

Negotiations are expected to begin today to form a coalition. As first party, Samaras will get three days to seek partners. If he fails, the mandate will go to the second party for a further three days, and then to the third party. If no deal can be reached, Greece heads to new elections.