SOFIA, Oct 1 (Reuters) - Bulgaria hiked electricity prices by nearly 10 percent on Wednesday in an effort to cut huge deficits in the Balkan country's energy sector, triggering protests in front of the state regulator's offices.
Hundreds of Bulgarians gathered outside the headquarters of the energy regulator in central Sofia, hurling eggs at the building and clashing with riot police.
Electricity costs are a politically sensitive issue in the European Union's poorest country where power bills consume a large slice of household income, especially in winter.
The previous Socialist-led government, which resigned in July, cut power prices twice during some 14 months in office, aiming to avert a repeat of street demonstrations against power prices which had toppled the previous centre-right government.
Even before Wednesday's hikes came into force, protests had flared in Sofia and in several other Bulgarian cities. The increases, described by the regulator as "inevitable", follow a recent announcement that state power provider NEK had accumulated debts of 2.9 billion levs ($1.9 billion).
Last month, Interim Deputy Premier Ekaterina Zaharieva said NEK was losing about 50 million levs a month, while giving preferential treatment to firms with political connections.
Interim Energy Minister Vasil Shtonov said the power price hikes will help inject more than 200 million levs into NEK.
Bulgaria is due to go to the polls on Sunday for its third election in just two years. The centre-right GERB party looks set to win, but might not secure an outright majority, raising the spectre of renewed political instability.
Bulgaria's three foreign-owned power distributors, controlled by Austrian EVN, Czech CEZ and Energo-Pro, said the price increase was "just a small step", adding that many of the regulatory problems they had complained about in the past still remained.
"The increase will only allow the companies to meet minimum costs for maintenance of the network and services to clients, but without an opportunity to upgrade and develop it," EVN's manager Ilina Stefanova said.
Bulgaria raised electricity prices by an average of 2 percent as of July 1. At the time, it was the first price rise approved by the regulator since June 2012.
In August, Bulgaria established an energy board with foreign representatives, aiming to assist the interim government in its attempts to stabilize the energy sector. ($1 = 1.5537 Bulgarian lev) (Reporting by Angel Krasimirov; Editing by Crispian Balmer)