Ukraine's battle fronts are shifting - interior ministry adviser

The southern city of Mariupol and a "corridor" between two eastern towns, Izyum and Volnovakha, are becoming the key battlefronts in Ukraine, an interior ministry adviser said on Thursday.

"(Russia) is withdrawing forces in the Kyiv region, but it's too early to say that the same is happening in the Chernihiv region," adviser Vadym Denysenko said.

Russia said on Tuesday it would scale down operations in the Kyiv and Chernihiv regions. NATO's chief said on Thursday this was a regrouping rather than a withdrawal.