Bulgarians voted Sunday to elect a new parliament, with Prime Minister Boyko Borisov's centre-right party tipped to finish first although it may struggle to find coalition partners.

Turnout is predicted to be low because of the coronavirus pandemic, with Bulgaria battling a third wave of infections that has seen hospital admissions spike.

Three hours after polls opened turnout stood at 7.58%, down from 8.44% at the same time during the last parliamentary elections in 2017.

Support for Borisov's GERB party - in power almost uninterrupted for close to a decade - has been eroded by a series of scandals, with protests last year accusing the government of protecting oligarchs.

Eve-of-ballot opinion polls gave GERB 28-29% of the vote, or an estimated 75-76 seats in the 240-seat legislature.

Three-time premier Borisov has refused all contact with the news media since the demonstrations.

Instead, he has been using social media to broadcast his unannounced campaign trail visits to the countryside under the slogan "Work, work, work!".

"I have always taken into account what the people decide... let the elections be honest," Borisov said after casting his vote in the absence of journalists.

"The immense support we received from our counterparts in Europe shows the importance of a stable European government in Bulgaria," he said in a statement on Facebook.

President Rumen Radev, who supported last year's anti-government protests and has been a frequent and vehement critic of Borisov's, said on Sunday that he had "voted against the destruction of the rule of law".

"These elections are a step towards returning to normality," he added.

'Fragmented opposition'

Up to six other parties are expected to win seats in parliament, said political analyst Antony Todorov, making it difficult to form the next cabinet.

"It's the absence of an alternative due to the fragmented and unconvincing opposition that explains GERB's hegemony," he added.

The number of voters will be among the most keenly watched aspects of the election and likely define the strength in the legislature of the new faces who have emerged from the protests.

Virus fears could impact the fortunes of the main opposition Socialists in particular, whose older electorate is more likely to abstain.

With 20 to 22% of intended votes, the Socialist party is likely to garner 54-56 seats.

A new populist group, There is Such a Nation, led by sharp-tongued talk show host and Borisov critic Slavi Trifonov, is polling third at around 13% and 33-34 seats.

Just behind it is the Turkish minority Movement for Rights and Freedoms party, a traditional kingmaker in several governments, with over 12% and 33-34 seats.

Two other formations will specifically target the votes of those who joined last year's demonstrations.

The right-wing Democratic Bulgaria coalition, whose leader Hristo Ivanov encouraged the protests, and the Stand up! Mafia out! left-wing coalition, close to Radev, are set to garner 5 to 6% of the votes and end up with 13-17 lawmakers each.

Ivanov said on Sunday he was hoping for a "parliament with more legitimacy to launch a debate on change".

Bringing up the rear is GERB's current government coalition partner, the nationalist VMRO party, which will most likely manage to cross the 4% threshold to enter parliament after an aggressive campaign of anti-Roma, anti-LGBT and anti-North Macedonia rhetoric.

Voting stations opened at 7am (0400 GMT) and will close at 8pm (1700 GMT) or no later than nine pm, if there are queues. Exit polls are expected shortly after.

First partial official results, usually expected late Sunday night, might be delayed due to the introduction of machine voting along with the usual ballot paper voting in the majority of big polling stations.

The central electoral committee is due to release full official results by Thursday.