Ukraine's President Volodymyr Zelenskyy has dismissed the commander of Ukrainian forces fighting Russian forces in the Donbas region in the country's east.

He has given no reason for the dismissal of Eduard Moskalyov announced on Sunday. He stressed his resolve to regain all occupied territories from Russia.

Ukrainian media say Moskalyov had served as the commander for Donbas since March last year, shortly after the Russian invasion began.

The dismissal comes as fierce battles continue to rage in Donbas, which covers the Donetsk and Luhansk regions.

Donetsk Governor Pavlo Kyrylenko wrote on social media on Sunday that Russian rocket strikes continued in his region from Saturday evening to Sunday morning.

He said the attacks killed three people and wounded four others in and near Bakhmut, one of Ukraine's regional strongholds.

In Ukraine, a number of high-ranking government officials have been replaced this year.