Ukrainian military officials say they have observed a buildup of Russian forces here.
Read here The invaders destroyed a part of the hospital in Mariupol
The most difficult situation now is, of course, in eastern Ukraine, he said in televised remarks.
"This is the Luhansk region — in the area of Rubizhne, in the area of Popasna … where there is, in fact, the destruction of cities. Unfortunately, the Russians continue to do everything they did before in Kharkiv, Sumy, Chernihiv, and so on — to destroy civilian infrastructure. And, of course, this is Mariupol, which is still under Ukrainian control and which is still fighting."
Recent advances by Russian forces in the Kharkiv region could be setting the stage for the eastern Ukrainian city of Sloviansk to become the next target of Russia's offensive, said the Institute for the Study of War, a Washington-based think tank.
"The situation now is very difficult in the direction of Sloviansk and Kramatorsk," Denysenko said. "These are the key points at this stage of this war. I believe, in fact, the results of at least this stage of this war will largely depend on the fighting in the east."
"All the humanitarian corridors that are being opened are officially declared by the state," he said. "Keep this in mind, and if you have the opportunity to go through these corridors — be sure to use them. Because we realize that the only strategy of the Russian Federation is the strategy of destruction of settlements."