Bulgaria's centre-right party and its main challenger, the Socialists, finished first and second in Sunday's parliamentary election, with neither one winning a majority needed to form a government, two exit polls indicated.
If that outcome is confirmed, it could lead to more political and economic instability in the Balkan nation.
Some 6.9 million eligible voters were choosing among candidates from 36 parties. But voter apathy was widespread and allegations of vote fraud and an illegal wiretapping scandal marred the campaign.
The Alpha Research exit poll said former prime minsiter Boiko Borisov's GERB party won 31.1%, with the Socialists second with 27.1%. A separate exit poll by Sova Harris said Mr Borisov's party won 31% of the vote, with the Socialists at 25.3%. Recent opinion polls had predicted that outcome.
With up to five other parties expected to enter the 240-seat parliament, formation of a stable government may prove difficult. "I expect that the country will soon head to another election," Anton Todorov, a political analyst, said before the vote.
Bulgaria has been led by a caretaker government since February when Mr Borisov, who guided his Citizens for Bulgaria's European Development party to victory in 2009, resigned as prime minister amid sometimes violent protests against poverty, high utility bills and corruption.
The former ruling party has seen its reputation tarnished further since prosecutors alleged that former interior minister Tsvetan Tsvetanov was responsible for illegally eavesdropping on political opponents during his term. Media leaks have also fuelled suspicion that Mr Borisov may have tried to interfere with the case.
But perhaps more than anything, Borisov's party may struggle to win the public's confidence due to economic issues. Six years after Bulgaria's entry into the European Union, the Balkan state of 7.3 million remains the bloc's poorest member.
Bulgarians have been angry over austerity measures designed to reduce public debt, which have meant cuts in health care and education programmes.