An overnight Ukrainian strike in the Russian border region of Belgorod killed five people and wounded 12 others, the region's governor announced early Sunday morning.

"To our great sorrow, the enemy shelling claimed the lives of five civilians," Governor Vyacheslav Gladkov said on Telegram. "As a result of the shelling, 12 people were wounded, including three minors."

One of the children was treated at the scene, while the two others were taken to hospital with "various shrapnel wounds", he added.

Seven of the adult victims were also hospitalised, with four of them in serious condition, Gladkov said.

Kyiv has stepped up its strikes inside Russian territory of late, particularly since launching a ground offensive into the nearby Kursk region earlier this month.

Gladkov declared in mid-August a state of emergency in Belgorod due in part to the Ukrainian bombardments, while Russia's defence minister said it was sending additional troops to the region to defend it in light of the incursion into neighbouring Kursk.