Two explosions took place in the early hours on Monday in Belgorod, a Russian region bordering Ukraine, but there was no damage or security threat, the top official in the area said.

Governor Vyacheslav Gladkov said he "wanted to dispel apprehensions among inhabitants of the region that someone or something flew in from the territory of Ukraine".

"That is not the case. Our military aviation was performing combat tasks as part of the special military operation," he added, using the official term by which Russia refers to the war in Ukraine.

The fact that he felt the need to reassure residents suggested a degree of nervousness among the population after a spate of fires and explosions in recent weeks at ammunition stores and fuel depots in Belgorod and other southern regions.

Ukraine has not directly accepted responsibility but has described the incidents as payback and "karma" for Russia's invasion.