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 the patients who died at St George Hospital 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.
There have been persistent reports of a shortage of ventilators in Russia, especially in the provinces - as President Vladimir Putin himself acknowledged last month, the BBC's Sarah Rainsford reports.
Production has increased rapidly, but research by the Reuters news agency found that outside Moscow many ventilators are old - made in the 1990s.
St Petersburg, with a population of approximately 4.9 million people, has 5,483 hospital beds for Covid-19 patients.
A police source quoted by Tass news agency said the ventilator which caught fire was new - it had been installed just this month - and was made by Russia's Ural machine-building plant.
St Petersburg has recorded just over 8,000 cases of Covid-19 so far - far fewer than Moscow, where the infection rate is continuing to climb at over 10,000 new cases daily.
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.
