There have been explosions in both the eastern Ukrainian city of Kharkiv and the western Russian city of Belgorod following a Russian airstrike, officials said.
According to regional military administrator Oleh Syniehubov, there were four injured civilians in Kharkiv, three men and one woman, he said on Saturday on Telegram.
Aerial bombs were also dropped on the village of Cherkassky Tyshky near the border, Syniehubov said.
There were also reports of a loud explosion on the opposite side of the border in Russia at around the same time, leading to some media outlets speaking of the possibility of a misdirected Russian bomb.
In Belgorod, the regional governor of the western Russian region, Vyacheslav Gladkov, said: "There was an explosion in Belgorod." Gladkov said he was on his way to the scene of the accident.
He spoke of five injured, but - in contrast to previous Ukrainian attacks - gave no details of the cause of the detonation. Pictures show severe damage.
In addition to a destroyed house, where the projectile hit, about 30 neighbouring buildings were also damaged.
The regional independent Telegram channel Pepel wrote: "A Russian aerial bomb probably fell on the house in Belgorod."
In the past, bombs intended for Ukraine have been accidentally released from Russian warplanes too early, causing destruction on Russian soil.
Recently, however, there have been reports that Russia is now increasingly using guided glide bombs that hit their target more accurately, even from a greater distance.
