MOSCOW – Electricity outages hit large sections of the Russian capital and nearby regions yesterday, forcing many subway lines and trolley buses to halt service while frustrated pedestrians tried to flag down taxis on traffic-jammed streets.

A spokeswoman for the country’s power grid, Magarita Nagoga of Unified Electricity Systems, said the outages stemmed from a fire and explosion at a substation.

The problems broke out late Tuesday and workers tried to repair the damaged equipment but were unable to get them into full operation before electricity demands hit their peak yesterday morning amid an early summer heat wave.

“We primarily believe that the main reason is that the equipment is worn out,” Ms. Nagoga said, noting that the substation was built in 1963.

The substation problem then caused a cascade effect in other parts of the grid. UES reported the spread had stopped by yesterday afternoon, news agencies said, but it was unclear when full service would be restored. Subways were being put back into service.

The problems extended as far as the Tula region, 120 miles south of Moscow, Energy Minister Viktor Khristenko told the lower house of parliament.

The Interfax news agency reported an explosion at a chemical factory in the Tula region that resulted from the power outage, sending nitric oxide into the air. Emergency officials were advising residents to stay inside their homes and shut their windows, the agency reported. UES chairman, Anatoly Chubais, said he took responsibility for the blackout after meeting with top government officials. President Putin, meanwhile, suggested that the UES management had neglected simple grid repairs and growing consumer demands.