The fire had not been contained as of Thursday morning, and more than 20 people were taken to hospital, the state news agency TASS reported, citing local officials.
Local authorities imposed a state of emergency in the region, located in western Russia.
The fire broke out Wednesday afternoon as strong winds spread a wildfire onto a military storage facility leading to “sporadic explosions” of ammunition, the Russian Defense Ministry said in a statement.
The depot can store up to 75,000 tons of munitions and housed 113 storage facilities with missile and artillery munitions, with some of the high-explosive ammunition contained in open storage, RIA Novosti agency reported, citing emergency services.
At least 14 villages were evacuated within a five kilometer radius of the depot, and a motorway was closed down, Reuters reported, citing the Interfax news agency.
More than 20 buildings burned down in two populated areas, the TASS news agency reported, adding that a criminal case had been opened.