Alexander Gusev, the Russian province's governor, said in a statement on Telegram that "explosive objects" had detonated after a fire in the region's Ostorogozhsky district.
He said there had been no casualties but that a state of emergency had been declared locally, with several hundred people relocated and a major road closed.
The Ukrainian source, speaking on condition of anonymity, told Reuters the operation was conducted by the SBU, Ukraine's internal security service.
"At this moment, there are still four pockets of a powerful fire observed at the site, as well as the unceasing detonation of munitions," the source said.
The source said the facility was in the village of Soldatskoe.
That settlement is about 130km from the nearest Ukraine-controlled territory.
Ukraine - which is restricted by some of its allies from using their missiles on Russian territory - has built up a stock of domestically produced long-range drones, some capable of hitting targets more than 1000km away.
Families have mourned troops killed in a missile attack on a military training facility in Poltava. (AP PHOTO)
Funeral services were held on Saturday for victims of one of the deadliest Russian air strikes since the war in Ukraine began as Ukrainian President Volodymyr Zelenskiy vowed to increase domestic military production by creating underground weapons factories.
The funerals took place in the eastern Ukrainian city of Poltava for the victims of a Russian missile attack on a military training facility that left more than 50 dead and about 300 injured.
Hundreds of mourners including grieving families, local residents and officials gathered at the Cathedral of the Assumption in the city, 350km southeast of Kyiv, for the solemn ceremony.
Sobbing relatives, many holding red carnations, stood over caskets placed outside the church, draped in yellow-and-blue Ukrainian flags.
Guards have taken part in a funeral ceremony of six Ukrainian servicemen killed in a Russian attack. (AP PHOTO)
An air raid siren sounded during the service.
Local residents knelt in silent tribute as hearses carrying the victims passed by on their way to a military cemetery outside the city for burial.
The sound of explosions thundered over the Ukrainian capital overnight as multiple Russian attack drones were intercepted by the city's air defences.
No injuries or serious damage were reported.
The Ukrainian Air Force said that 67 drones were launched over the country overnight, with air defences active in 11 regions.
Fifty-eight drones were shot down, with three more destroyed by electronic weapons systems, it said.
with AP
