At least five people were killed and 10 or more injured in an explosion at a gas station in the city of Makhachkala in the southern Russian region of Dagestan on Monday evening, the Tass news agency reported, citing a local disaster response group.
An unconfirmed report by another Russian news agency, Ifax, said the death toll could reach 25 or more, according to Reuters, with perhaps 60 or more people injured.
The cause of the blast and resulting fire was not yet known.
According to the authorities, there was a risk of further explosions and fires, the RIA news agency reported.
Dagestan, a mostly Muslim region in the south of Russia on the northwest coast of the Caspian Sea, is known for the stark beauty of its mountain landscapes, for its many small ethnic groups and for a violent and long-simmering Islamist insurgency.