A fire at a St Petersburg hospital has killed five coronavirus patients in an intensive care unit.
The blaze was apparently started by a short-circuit in a ventilator, Russian news agencies reported.
The fire was quickly put out and 150 people were evacuated from the hospital, the country's emergency ministry said. It is not clear how many people have been injured.
All of the patients who died had been on ventilators.
"The ventilators are working to their limits. Preliminary indications are that it was overloaded and caught fire, and that was the cause," a source at St Petersburg emergencies department told the Interfax news agency.
Russia's NTV news website reports that the fire did not spread beyond one small Covid-19 ward on the sixth floor.
It quotes doctors as saying a short-circuit caused a ventilator "literally to explode" because of the oxygen concentration, and the ward filled with smoke, which suffocated the patients.
St Petersburg, with a population of approximately 4.9 million people, has 5,483 hospital beds for Covid-19 patients.
State investigators have opened a case to determine whether there was criminal negligence – either in the ventilator design and manufacture or in the hospital's fire precautions.
The city has Russia's third-highest infection rate, with 7,700 infected patients and 56 recorded deaths.
The St George Hospital in the Vyborg district had been converted to a Covid-19 hospital at the end of March.
The emergency services sent 105 firefighters and 55 vehicles to the hospital, offficials said.