Russia’s Emergency Ministry reported that a total of 105 people were injured, and 30 of them died.
Three of those killed were children, Dagestan’s governor Sergei Melikov said.
The explosion took place Monday night on the outskirts of Makhachkala, the region’s capital. A fire started at a car repair shop and spread to a nearby gas station, prompting a blast, Russia’s state news agency RIA Novosti reported, citing the country’s Emergency Ministry.
The subsequent fire raged on an area of 600 square meters (6458 square feet), the report said.
Some of those injured will be airlifted to Moscow for treatment, according to the report.
Russian authorities have begun a criminal investigation.
Families of the victims will receive 1 million rubles (about $10,000) each, Dagestan’s authorities said, and those injured – 200,000-400,000 rubles.
Tuesday in Dagestan has been declared the day of mourning.
The explosion occurred at an oil mine in the Khanty-Mansiysk region late in the evening, local authorities said.
Across Russia, in western Siberia, another blast killed two people and wounded five more on Monday night.