Updated 12.30pm

Russia said Wednesday that everyone on board a military transport plane -- reportedly carrying dozens of captured Ukrainian soldiers -- had died after the aircraft crashed near the border with Ukraine.

"Everyone on board died," the Belgorod regional governor Vyacheslav Gladkov said on social media. The Russian army earlier said 65 Ukrainian captive soldiers were onboard. 

Russia said Wednesday that the IL-76 military transport plane had crashed in the western Belgorod region, bordering Ukraine.

Unverified videos on social media showed a large plane, purportedly in the Belgorod region, falling from the sky on its side before crashing in a fireball.

"At around 11am Moscow time (0800 GMT), an IL-76 aircraft crashed in the Belgorod region during a routine flight," Moscow's defence ministry was quoted as saying by the RIA-Novosti news agency.

"On board were 65 captured Ukrainian army servicemen being transported to the Belgorod region for exchange, six crew members and three escorts," it said.

AFP was not able to immediately verify Russia's claim.

The crash occurred in the Korochansky district, northeast of the region's capital, regional governor Vyacheslav Gladkov said on Telegram.

"Now an investigation team and emergency services are working on the site. I have changed my working schedule and travelled to the district," Gladkov said.

There was no immediate official reaction in Kyiv, but local media cited sources in Ukraine's defence forces as saying that its armed forces downed the plane, and that it was transporting missiles.