At least five people were killed and seven injured in an explosion caused by gas leak in an apartment building in Russia's city of Saratov on Friday, the Emergency Situations Ministry said. 

Search and rescue operations continue, and more people could be under the rubble, the ministry said, adding that some 20 specialists, search dogs, and eight units of equipment are deployed at the scene. 

Based on preliminary data, more than 30 apartments may be damaged or destroyed, and there is a threat of further collapse, according to the ministry. 

The authorities declared a regime of regional emergency following the incident.