SOFIA: Tens of thousands of Bulgarians protested in more than 20 cities against high electricity bills on Sunday, piling pressure on the government after a week of persistent demonstrations.

Protesters chanting "It will be the same every day until we win," paralysed city centres and demanded the resignation of the cabinet and the re-nationalisation of power distributors.

Electricity prices are politically sensitive in the European Union's poorest member since power bills bite off a big chunk of monthly incomes, especially during the winter.

Demonstrators threw eggs, bottles and fruit, burned their electricity bills and attacked the offices of power firms in five cities. More than 2,000 people blocked the highway to Greece near the southern town of Dupnitsa.

In the capital Sofia, protesters blocked traffic on the famous Eagles' Bridge and along several main roads.

"We cannot stand it anymore," said Penka Slavova, a pensioner. "My pension is 155 levs ($110) and my December bill was 175 levs. What should I do?"

Local media reported that protesters, including women and children, clashed with police when trying to reach the headquarters of Czech firm CEZ which supplies power to Sofia and northwestern Bulgaria.

Bulgaria's power distribution market is divided into three regions, controlled by CEZ and fellow Czech firm Energo-Pro and Austria's EVN.

Despite enjoying relative economic stability since the global financial crisis erupted, Bulgarians face low living standards compared to other EU members. Monthly pay averages 400 euros, just a fraction of the EU norm, while the average monthly pension is $176.

The government has said it will look into the issue of rising electricity bills, but Finance Minister Simeon Djankov on Wednesday ruled out the re-nationalisation of power firms.

"There is no such possibility and I don't think any European Union member can afford to talk about nationalisation," Djankov told the state television BNT.

RULING PARTY SUPPORT WANES

Support for the ruling centre-right GERB party, led by Prime Minister Boiko Borisov, fell to 22.6 percent in February, down from 23.8 percent in January due to delayed reforms, low incomes and a lack of action to root out corruption. Unemployment is at a 10-month high.

Backing for the opposition Socialists, who said they would consider re-nationalisation of the power distributors if they win the parliamentary elections on July 7, rose to 22.1 percent.

"We should remember this date - February 17," said political scientist Evgeniy Daynov of Sofia's New Bulgarian University.

"This is when the ruling GERB party died. This is a protest against the oligarchic model of GERB rule, which is nothing more than the plundering of the state to benefit the oligarchs."

Police ordered a bus to park across one Sofia street to stop protesters reaching the president's office. A few stones were thrown in the direction of the building.

In one of the biggest rallies, more than 10,000 people filled the city of Varna on the Danube River, where the national flag had been lowered at the municipality in support of the protests. ($1 = 1.4650 Bulgarian levs)