Russian forces shelled dozens of towns in the Donbas and were inching closer to encircling two key cities in the region where thousands of civilians are in danger of being trapped without a way out, Ukraine’s military said.

President Volodymyr Zelenskiy, meanwhile, blasted suggestions that Ukraine make territorial concessions to Russia to end the war, likening the idea to the West’s appeasement of Nazi Germany in 1938.

Russian forces shelled 40 towns in the easternmost pocket still held by Kyiv in the Donbas, Ukraine’s military said on May 26.

Russian forces were advancing on the key twin cities of Severodonetsk and Lysychansk on both banks of the Siverskiy Donets River, with the fighting reaching the limits of Severodonetsk.

“Russian troops have advanced far enough that they can already fire mortars” on the city, the governor of the Luhansk region, Serhiy Hayday, said in a statement on social media.

The fall of the two cities would leave the whole of the Luhansk region under Russian control, one of the Kremlin’s stated goals in its war.

Police in Lysychansk are collecting bodies of people killed to bury them in mass graves, Hayday said. Some 150 people have been buried in a mass grave in one Lysychansk district, he added.

Moscow-backed separatists quoted by Russian news agency TASS claimed on May 26 that they were holding about 8,000 Ukrainian prisoners of war, but the claim could not be independently confirmed.

Oleksiy Arestovych, an adviser to Zelenskiy, said Russia’s “army is having some tactical success, which is threatening to become an operational success in the direction of Lysychansk and Severodonetsk.”