Bulgaria's former Premier Boyko Borisov (AP)

The party of conservative former Premier Boyko Borisov has come first in Bulgaria's general election Sunday, according to an exit poll, although he now faces a struggle to find coalition partners.

According to the poll, Borisov's GERB party has won around 25% of the vote, followed by the party of his centrist rival Kiril Petkov on around 19%.

On Sunday, Borisov, 63, considered that he was Bulgaria's "most experienced" politician and stressed the country's European Union and NATO allegiances.

He held power three times and dominated politics for a decade and is now eyeing a comeback on a "return to stability" platform.

Bulgarians voted on Sunday in their fourth general election in 18 months, anxious about soaring consumer prices and energy costs ahead of a winter overshadowed by the Ukraine war.

While endemic corruption was the focus of the previous vote last November, economic woes are now top of voters' concerns.

The European Union's poorest member state is battling annual inflation of close to 20%.

Krasimira Velkova, a 64-year-old economist who cast her ballot in Sofia, confirmed these fears.

"People worry about inflation, about the fact that when you enter a food store, a shopping trolley that's just half full costs a fortune. The difference compared to last year is absolutely staggering," Velkova told AFP.

"We are worried about how we'll get through the winter," she added.

Bulgaria dogged by political instability

The Balkan country has been dogged by political instability since early last year when GERB lost power following massive anti-corruption demonstrations.

Borisov's rival, outgoing reformist Premier Kiril Petkov, 42, has urged voters to let him "continue the change" he started under a "zero corruption" slogan.

Petkov, a Harvard-educated former entrepreneur, stormed onto the political scene in 2021, but his precarious four-party coalition was toppled in a no-confidence motion after just seven months in power.

He urged people on Sunday "to make the important choice... to move forward towards a new, prosperous, capable and transformed Bulgaria."

His government had offered substantial rises in pensions, and Petkov said he was planning a rise in the average salary in Bulgaria, which now stands at 870 euros ($853), the lowest in the 27-nation EU.

Borisov open to talks with anyone on forming cabinet

Petkov categorically ruled out forming a coalition with Borisov, heightening fears that the vote may fail to end the country's worst period of political instability.

On the other hand, Borisov repeated once again on Sunday that he would be open to talks with anyone on forming a cabinet for the sake of stability amid the war in Ukraine and people's fears about rising inflation.

"What's important for us is for reason to prevail... Believe me, right now I am the most well-meaning and open person to all parties," Borisov considered.

The protracted political instability has left Bulgaria struggling to pass reforms and has hampered economic growth.

Voter fatigue was also high, analysts said. By 4:00 pm, turnout was just over 25% of eligible voters -- roughly the same as during the vote in November 2021.