SOFIA, Bulgaria (AP) -- Thousands of miners at Bulgaria's three largest coal mines walked off the job Monday, claiming that employers are not delivering on their promise of bonuses.
Some 1,500 miners halted work at state-owned company Maritsa Iztok's open-pit mines late Sunday, union leader Gencho Genchev said.
Strikers are demanding a euro500 ($633) cash bonus due to increased output at the mine and say management earlier promised the bonus for all 7,100 miners. But, the company says it can only pay bonuses to those directly involved in the production process without putting itself into financial danger.
Energy Minister Traicho Traikov estimated the strike would cost the company up to euro1.5 million a day.
The mining company says more than 33 million tons have been mined in 2011, well above the production target of 27 million tons. It supplies 90 percent of all lignite coal used for electricity production in Bulgaria.
Four major coal-fired thermal power plants located in the Maritsa Iztok complex, including two owned by U.S. energy companies AES and ContourGlobal, rely completely on the mines for their output, which covers a quarter of the country's electricity needs.
Assuaging fears of possible power outages in the country, Traikov said there were enough power generating capacities that would be switched on gradually. He warned, however, that then consumers would have to pay more for electricity.