Preliminary results of parliamentary elections held here Sunday indicated that neither of the two leading parties garnered a strong mandate to govern Bulgaria or build a lasting coalition, an outcome likely to prolong the period of political instability in the European Union's poorest member.

The right-leaning Citizens for European Development of Bulgaria, or GERB, won about 30% of the vote, according to an exit poll cited on Bulgarian National Television, a public broadcaster. Its most powerful opponent, the Socialist Party, won some 25%.

Bulgarians are holding early elections to the National Assembly, the country's unicameral parliament, after the GERB-led government of Prime Minister Boyko Borisov stepped down in February amid nationwide protests.

Even though Mr. Borisov's party has likely won the highest number of votes, it won't have enough seats in parliament to govern alone, according to the exit poll. The Movement for Rights and Liberties, a party comprised mostly of Bulgarians of Turkish ethnicity, won some 10% of the vote, while the country's largest nationalist party, Ataka, won 8%. None of the other parties in the race likely passed the 4% threshold that would entitle them to get parliamentary seats, according to the poll.

Parliament is expected therefore to be less fragmented than previously thought, but with no clear political allies, Mr. Borisov's party will struggle to form a government despite winning the most votes. The three other parties likely to make it to parliament have said they wouldn't support the ex-prime minister.

A former bodyguard to the country's Soviet-era dictator, Mr. Borisov has pledged to continue an austerity drive out of the desire to keep the national currency, the lev, pegged to the euro.

His fall from power happened amid fiery protests and several self-immolations by people who claimed the country was gripped by poverty.

The Socialists said the former government hasn't taken into account the social cost of budget austerity.

The two main contenders in the vote traded blows over the weekend over several hundred thousand ballots the authorities seized from a printer and said were questionable. The Socialist leader, Sergei Stanishev, said his rival was planning to use the ballots to rig the vote, a claim Mr. Borisov rejected.

Despite concerns of attempted manipulation of the election by various parties, "the state prosecutor and other institutions are doing their jobs," said Thomas Rymer, spokesman for the Organization for Security and Cooperation in
Europe , or OSCE, which sent more than 200 observers to monitor the vote. Once the results are in and verified, the OSCE will Monday say whether the election proceeded fairly, he added.

Bulgarian President Rosen Plevneliev earlier in the day urged voters to go to the polls, saying that attempts to manipulate the outcome will fail as the country's institutions are ensuring the elections take place fairly.

While the vote appears to be going smoothly, local media have reported that nationwide 17 people had been arrested for trying to pay citizens to cast votes for particular parties.

Iva Pavlova, 63 years old, said that "the political situation is very complicated, but I expect better things will come" and added that reports of some illegally produced ballots being confiscated by authorities is actually encouraging because it shows that "the state prosecutor is finally doing its job."

Konstantin Dragnev, 82, voting in central
Sofia , said that he was shocked by all the fraud allegations, wire-tapping and extra ballot scandals. But he takes it in stride. "Generally, this kind of stuff always happens, it's just mudslinging."