Gas explosion wrecks apartment block in Samara
It's believed the explosion took place on the second floor of the five-storey block, leading to a partial collapse of the brick building.
One of the four people injured is in a serious condition with 95 per cent burns.
It is thought that around 40 people were living in the building, which is divided into 21 flats.
Investigators say a gas leak is the most likely cause of the explosion.
A criminal case has been opened on suspicion that safety regulations may have been breached.
Around 150 workers are involved in the clean-up operation.