Russia said one of its fighter jets lost ammunition over Belgorod near the Ukrainian border on Thursday, after local authorities reported a blast that injured two people and left a huge crater in the city.
Russian jets have regularly flown sorties over Belgorod since the launch of Moscow's offensive in Ukraine in February 2022.
On Thursday evening, local officials reported a massive explosion in Belgorod, saying the blast had left a crater in the city centre and injured two women.
Vyacheslav Gladkov, governor of the region of Belgorod, said the blast had sent a shock wave that damaged four apartments and four cars and downed power line poles.
"An explosion took place," Gladkov said on the Telegram messaging app, adding that investigators and representatives of the emergencies ministry were at the scene.
He said that as a result of the explosion, a "huge" crater some 20 metres wide (65 feet) had appeared in the city centre.
Gladkov and Belgorod's mayor, Valentin Demidov, posted pictures of damage on social media.
One picture showed grim-looking locals huddling outside an apartment building, with one woman holding a small dog, and a fire engine nearby.
Other images showed apartment interiors wrecked by the blast.
Local authorities did not say what caused the blast, but the Russian defence ministry released a statement saying a fighter aircraft had lost ammunition over Belgorod.
"During the flight of the Su-34 aircraft of the aerospace forces over the city of Belgorod, an abnormal descent of aviation ammunition has occurred," the ministry said.
The statement carried by Russian news agencies added that the incident had taken place at 22:15 local time.
Citing preliminary information, Gladkov said one woman was hospitalised with a head injury, while another woman was treated at the scene.
Demidov said residents of the damaged buildings would be temporarily moved to hotels.
The region of Belgorod has been repeatedly shelled since Russian President Vladimir Putin sent troops to Ukraine in February 2022.
In January, Gladkov told Putin that 25 people had been killed and more than 90 injured in the region since the start of the offensive.
In October 2022, an SU-34 jet crashed into a residential building in the southern city of Yeysk, also near the border with Ukraine, killing 16 people, including several children.