At least 30 people were killed and more than 100 injured when a fire caused an explosion at a gas station in the southern Russian republic of Dagestan, local authorities said.

The blaze started at a car repair shop on Monday night then spread to the nearby fuel station on the outskirts of Dagestan's capital of Makhachkal, Russia's emergency situations ministry said.

Search and rescue efforts were ongoing as of Tuesday morning, with emergency workers clearing the rubble and searching for potential survivors, state media agency TASS reported.

Several children were among the dead, according to the head of the Dagestan republic, Sergey Melikov, and at least three bodies were recovered from the rubble, TASS reported.

Russia's Investigative Committee launched a criminal investigation into the deadly blaze, state media agency RIA Novosti reported Monday.

A statement from the Kremlin said Russian President Vladimir Putin "expressed condolences to the families and friends of those killed in the explosion at a gas station in Makhachkala, and wished a speedy recovery to the victims."

Dagestan's head of government Abdulmuslim Abdulmuslimov visited the site of the disaster in in Makhachkala on Tuesday.

The Dagestan government declared Tuesday a day of mourning, TASS reported.