The blaze started at a car repair shop on the roadside of a highway in Dagestan capital Makhachkala before spreading to a nearby petrol station, officials said.

Footage posted online showed a one-storey building ablaze.

"It's like a war here," said a witness to the fire in the southern Russian region.

The number of people injured rose to 66, 10 of whom are in a critical condition, the Russian deputy health minister Vladimir Fisenko said.

Thirteen of the wounded are children, according to the Dagestan health ministry.

It took fire fighters more than three and a half hours to put out the fire that spread into an area of 600 sq m, TASS reported, citing a statement from the Russian emergency service.