The injured were taken to hospital after the blast early on Sunday, though some residents refused to leave what was left of their property.
The explosion in a high-rise apartment building in the south of the city was probably caused by gas despite initial police fears it might have been a bomb.
One police official said that "first testimonies and the nature of the damage" pointed to a gas explosion.
The Moscow regional office of the FSB security agency also said the blast had been caused by a gas explosion.
FSB spokesman Viktor Zakharov said: "We are trying to establish whether it came from a gas pipe or a cylinder."
The coming elections have meant
a heightened state of alert
The blast occurred around 04:00 (01:00 GMT) and destroyed at least one apartment completely.
Rescuers evacuated the rest of the building and police sealed off the surroundings.
Security had been stepped up across Russia amid fears of attacks in the run-up to the 14 March presidential poll, in which President Vladimir Putin is all but certain to win re-election to a second term.