Authorities said the fire at the arsenal in the Ryazan region that holds munitions had been sparked by burning grass. Television footage showed smoke rising high across the skies, and powerful blasts shook the area about 250 kilometers (155 miles) southeast of Moscow.
Regional officials have ordered the evacuation of more than 2,300 people from 10 nearby villages. Six people have been hospitalized with injuries.
The Defense Ministry said that 189 troops backed by four heavy firefighting planes, three helicopters and drones were deployed to help contain the blaze. A deputy defense minister arrived in the area to coordinate emergency efforts.