Russian defense minister Sergei Shoigu has visited the Russian-occupied Ukrainian port city of Mariupol, in an apparent attempt to show that the eastern Donbas region is under Moscow's control.

The defense ministry said on Monday that Shoigu inspected construction work underway to restore infrastructure in Donbas.

Mariupol is about 180 kilometers south of Bakhmut, the strategic city Russia is trying to capture by intensifying attacks against defending Ukrainian forces.

But the head of the Russian private military company Wagner wrote on social media on Sunday that troops on the frontline have not received ammunition needed for operation, indirectly criticizing the ministry's response.

Meanwhile, Ukrainian President Volodymyr Zelenskyy said on Sunday that fighting in Donbas is one of the hardest battles.

He stressed that Ukrainian forces will continue to fight back.