Bulgaria's centre-right party GERB and its main challenger, the socialist party BSP, have finished first and second in parliamentary elections, with neither one winning a majority needed to form a government, two exit polls show.

If that outcome is confirmed, it could lead to more political and economic instability in the Balkan nation.

About 6.9 million eligible voters chose from among candidates from 36 parties in Sunday's elections. But voter apathy was widespread, and allegations of vote fraud and an illegal wiretapping scandal marred the campaign.

Al Jazeera's Jonah Hull, reporting from Sofia, said that the exit poll data is not a foregone conclusion by any means.

He said with the turnout being just 48 percent, 12 percent lower than the election in 2009, any high hopes that came with the EU membership are gone. Hull said given the myriad problems in terms of economy, corruption and organised crime, the broad consensus is that not much is likely to change.

The Alpha Research exit poll said former prime minister Boiko Borisov's GERB party won 31.1 percent, with the BSP party coming in second with 27.1 percent.

A separate exit poll by Sova Harris said Borisov's party won 31 percent of the vote, with the Socialists at 25.3 percent.

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.

Caretaker government

Bulgaria has been led by a caretaker government since February, when 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 ex-ruling party has seen its reputation tarnished further since prosecutors alleged that Tsvetan Tsvetanov, former interior minister, was responsible for illegally eavesdropping on political opponents during his term.

Media leaks have also prompted suspicion that 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.

Many Bulgarians feel squeezed by low wages - the lowest in the EU at 400 euros ($524) a month - and relentless inflation. They feel betrayed by promises that joining the EU would bring them a better life.

Now, more than 22 percent of the people live below the official poverty line.

According to official statistics, the unemployment rate is 12 percent, but experts suggest that the real rate is more than 18 percent.

Allegations of vote-rigging that have accompanied elections in the past prompted five major former opposition parties to seek an independent vote count; the first such count since 1990, to be conducted by the Austrian agency SORA.

More than 250 international observers monitored Sunday's election.

On Saturday, prosecutors stormed a printing house and seized 350,000 ballots that were printed over the legally fixed number.

The country's president urged Bulgarians to vote in large numbers to counter possible vote-buying practices that could influence the outcome of the race.