Two Russian villages were evacuated on Thursday after a fire broke out at an ammunition depot near the border with Ukraine, local authorities said.
The blaze comes days after explosions at a military base and munitions depot in Crimea, the Ukrainian peninsula annexed by Moscow, which Russia called an act of "sabotage" by Kyiv.
No casualties were reported, but residents of Timonovo and the nearby village of Soloti were "moved to a safe distance", he said, adding that authorities were investigating the cause of the fire.
A video posted on social media showed a huge fireball billowing a thick column of black smoke.
Another video showed several explosions in quick succession in the distance.
Thursday's fire comes amid a slew of blasts at Russian military installations near Ukraine.
Earlier this month, a bomb exploded near the Saki military airfield in Crimea, killing one person and injuring several others.
In the second case, Moscow unusually admitted there had been an act of "sabotage".
Since the start of the Russian offensive in Ukraine in late February, Moscow has repeatedly accused Ukrainian forces of carrying out strikes on its soil, particularly in the Belgorod region.
Last month, missiles slammed into the provincial capital Belgorod, killing four people, according to local authorities.
Earlier this month, Gladkov accused Ukraine of carrying out an attack on a fuel depot in Belgorod with two helicopters.