Bulgaria's government has resigned after violent nationwide protests against austerity and high electricity prices.

Many Bulgarians are deeply unhappy over high energy costs, power monopolies, low living standards and corruption.

Tens of thousands of Bulgarians have rallied in cities across the country since Sunday in protests which have turned violent, chanting "Mafia" and "Resign".

Prime Minister Boiko Borisov tried to calm protests by sacking his finance minister and pledging to cut power prices, but the measures failed to defuse discontent.

"I will not participate in a government under which police are beating people," Mr Borisov said as he announced his resignation this morning.

Parliament is expected to accept the resignation later in the day.

Mr Borisov, a former bodyguard to communist dictator Todor Zhivkov, can now try to form a new government, using his GERB party's strong position in parliament.

If he fails, an election scheduled for July may be brought forward.

GERB's popularity had held up well until late last year because austerity measures were relatively mild compared with many other European countries, with salaries and pensions frozen rather than cut.

In the last opinion poll, taken before protests grew last weekend, the opposition Socialists were nearly tied with GERB.

Many Bulgarians are feeling frustrated with unemployment hitting a ten-month high of 11.9% and the average salary stuck at 800 levs (€400) a month.

Frustrations boiled over when heating bills rose during the winter.

Bulgaria raised the costs of electricity - politically sensitive since bills eat a huge part of modest incomes - by 13% last July, but the real impact was not felt until households started using electrical power for heat in winter.

Mr Borisov has said the electricity distribution licence of central Europe's largest listed company, Czech-based CEZ will be revoked, setting Bulgaria on a collision course with the Czech Republic, which owns 70% of the company.

The Czech government has already stepped into a row between the company and Albania, which revoked the company's licence last month.

Czech Prime Minister Petr Necas said Bulgaria's move was highly politicised and asked for an explanation.