The governor of a Russian border region accused Ukraine of shelling an apartment block there on Thursday but a Kyiv official said a stray Russian missile was to blame.
Vyacheslav Gladkov said a school had been damaged in a village close to the border, and that the top floor of an apartment block had been struck in the city of Belgorod.
Ukrainian presidential adviser Mykhailo Podolyak said on Twitter that Russia had launched a missile towards the Ukrainian city of Kharkiv but "something went wrong and it hit (a) residential building".
Video showed rubble next to a 16-storey apartment block with a large rupture near its roof. Reuters could not independently establish who was to blame for the incident, in which Gladkov said no one had been hurt.
The governor of another Russian region, Kursk, said an electricity substation had been damaged by a shell, which had knocked out power to two settlements. Reuters was not able to independently verify that report.
Russian investigators said they had opened a criminal case into the shelling of the region and blamed the Ukrainian military. Ukraine's defense ministry did not immediately reply to a request for comment.
Russia's border regions have reported sporadic attacks since the invasion of Ukraine in February, including on targets such as fuel and ammunition stores. Ukraine has not admitted responsibility, but an official has described previous incidents as "karma" for Moscow's war actions.