MOSCOW (AFP) - Four people died and at least six were taken to hospital suffering from smoke inhalation after a fire broke out in a Moscow retirement home, investigators said on Thursday (April 9).

Residents at the private care home in the city's north-west pleaded for help from windows as thick smoke filled the building, a source in emergency services told TASS state news agency.

There were more than 50 people in the facility when the fire broke out Wednesday evening, Russia's Investigative Committee, which probes serious incidents, said in a statement.

"As a result, four people died, six were taken to medical facilities suffering from smoke inhalation," it said, while the numbers of injured are still preliminary.

Interfax news agency cited a source as saying that a total of 15 of the injured, who are aged from 66 to 90, were hospitalised in a serious condition and four need ventilators to breathe.

The Investigative Committee said a criminal inquiry would assess whether the deaths had been caused through negligence and whether there had been breaches of fire safety rules.

While fires often break out in dilapidated state-run facilities for the elderly and people with disabilities, the Third Age company that runs the care home advertised it as a "premium quality" facility where residents can get massages or aromatherapy.

Moscow deputy mayor Pyotr Biryukov said the fire was believed to have started in a basement boiler room when diesel fuel exploded, the RIA Novosti state news agency reported.

One of those who died was reportedly working in the boiler room.

Mayor Sergei Sobyanin tweeted the blaze was sparked by a cable in the basement catching fire.