Thousands of Bulgarians protested on Sunday against rising electricity and heating bills, and police clashed with demonstrators throwing eggs and tomatoes at government buildings.
The violence occurred in Sofia, the capital, when riot police struggled to keep demonstrators away from public buildings, but no injuries were immediately reported. Large parts of the city center remained blocked off for hours.
Similar rallies occurred in other cities across the country, with some temporarily blocking traffic on major highways.
Earlier, the protesters in Sofia burned their utility bills in public, accusing the government of failing to improve their falling living standards and demanding the expulsion of the three foreign-controlled power distributors that control the local market: CEZ and Energo-Pro from the Czech Republic, and Austria's EVN.
In January, Albania revoked the license of CEZ and announced that electricity distribution would return to government control, but experts in Bulgaria have expressed doubt the government can legally do that.
Bulgaria, which joined the European Union in 2007, is the bloc's poorest member country, with an average monthly salary of €360 ($480) and an average pension of €150 ($200).
The ruling center-right party of Prime Minister Boiko Borisov, which won parliamentary elections in 2009, has been steadily losing public support in the wake of the country's worst economic downturn in a decade.
Elections in July are expected to be a close race between the incumbents and the opposition Socialist party.