At least four people have died after an apartment building partially collapsed following an apparent gas explosion in Russia.

Authorities said four others were injured and in hospital, while 68 residents remained unaccounted for in the incident in Magnitogorsk, a city of 400,000 about 870 miles southeast of Moscow.

Some residents could have been buried under debris after the accident, officials added.

Cries for help could be heard from the rubble, local news reports said. Witnesses apparently reported being able to smell gas in the area.

It happened around 6am on Monday – a public holiday in Russia – when most residents were still asleep.

The Investigative Committee said the collapse of a section of the 10-storey building was apparently caused by a gas leak.

Of more than 100 apartments in the building, 48 were damaged, the Emergencies Ministry said.