MOSCOW - A Russian warplane accidentally fired a weapon into the city of Belgorod near Ukraine late on Thursday, causing an explosion and damaging buildings, Tass cited the defence ministry as saying.

Local authorities reported a large blast in the city, which lies just across the border from Ukraine. The regional governor said two women had been injured.

"As a Sukhoi Su-34 air force plane was flying over the city of Belgorod there was an accidental discharge of aviation ammunition," Tass cited the defence ministry as saying.

It did not say what kind of weapon was involved.

The Su-34 is a supersonic fighter-bomber jet.

The ministry said some buildings had been damaged and announced a probe was already under way, according to Tass.

Belgorod region governor Vyacheslav Gladkov, announcing a state of emergency, said on Telegram there was a crater measuring 20 metres (65 feet) across on one of the main streets. Four cars and four apartment buildings were damaged, he added.

Video footage from the site showed piles of concrete on the street, several damaged cars and a building with broken windows. One shot showed what appeared to be car upside down on the roof of a store.

The Belgorod region is one of several parts of southern Russia where targets such as fuel and ammunition stores have been rocked by explosions since the start of what Moscow calls its "special military operation" in Ukraine on 24 February 2022.