Three people died and several were injured after a gas explosion rocked a block of flats in the Russian city of Magnitogorsk, emergency services reported.

"Three alive and three dead were taken from under the debris. The fate of 79 people is incomprehensible", Chelyabinsk Region's deputy governor Oleg Klimov told reporters.

All those killed were adults, he said, adding that three injured, including one child, were taken to hospital, Sputnik reported.

A criminal probe has been opened into a blast that tore down a part of an apartment building in the Russian city of Magnitogorsk in the southern Urals, the Investigative Committee spokeswoman said.