Russian strikes killed at least nine people in Ukraine overnight to Sunday, officials said, as Kyiv and Moscow traded fire amid an ongoing major prisoner swap.

Four people were reported dead in the western Khmelnytskyi region, four in the Kyiv region — which came under attack for the second night running — and one in Mykolaiv in the south.

"Last night, the Khmelnytskyi region came under hostile Russian fire, which resulted in the destruction of civilian infrastructure. ... Unfortunately, four people were killed," Sergiy Tyurin, the deputy head of the regional military administration, said in a Telegram post.