Five people died in a fire in a hospital for coronavirus patients in Russia's second city of Saint Petersburg on Tuesday, with some victims attached to ventilators, officials said.

Emergencies personnel work at the site of a fire at the Saint George hospital in Saint Petersburg on May 12, 2020. Photo by AFP.

Another 150 people were evacuated after the blaze broke out on the sixth floor of the Saint George hospital, the emergencies ministry said, one of a string of fires in care facilities and clinics in Russia in recent days.

The hospital had been repurposed to treat coronavirus patients and some of the dead patients had been connected to ventilators when the fire began.

Windows near the top floor of the hospital were blackened with soot as firefighters worked outside.

Four patients died in an intensive care ward, the city's Vyborg district attorney Pavel Danilov told AFP, adding that the cause of death of the fifth person was being clarified.

"Everyone is shocked by what happened," said Svetlana Stepanova, a pensioner receiving treatment at the hospital.

"A fire in the hospital is a nightmare," she told AFP.

Saint Petersburg governor Alexander Beglov, citing preliminary information, said a short circuit was believed to be the cause of the fire.

"A ventilator has caught fire," his office said in a statement.

Russia's Investigative Committee, which examines serious crimes, said it had launched a probe into the incident.

A fire at a Moscow hospital treating coronavirus patients last week killed one person and forced hundreds of others to evacuate.

On Monday, a fire broke out in a retirement home in the Moscow region, killing nine people. 

Two more people died in hospital later, officials said on Tuesday, bringing the total death toll to 11.

Russia reported 10,899 new coronavirus cases on Tuesday, continuing a steady increase of new infections that has seen the country become a global virus hotspot.

With a total of 232,243 infections, Russia is among the top four most infected countries in the world alongside the United States, Spain and Britain.

Russia's reported mortality rate is much lower compared to other European countries hit hard by the pandemic, with 107 new deaths and 2,116 dead from the coronavirus as of Tuesday.