Ukrainian President Volodymyr Zelensky on Saturday warned his people that Russian forces, who were retreating from Ukraine, were creating “a complete disaster” outside the capital as they leave mines across “the whole territory,” even around homes and corpses.

The Ukrainian President issued the warning as the humanitarian crisis in the encircled city of Mariupol deepened, with Russian forces blocking evacuation operations for the second day in a row, and the Kremlin accused the Ukrainians of launching a helicopter attack on a fuel depot on Russian soil.

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Ukraine denied responsibility for the fiery blast, but if Moscow’s claim is confirmed, it would be the war’s first known attack in which Ukrainian aircraft penetrated Russian airspace.

“Certainly, this is not something that can be perceived as creating comfortable conditions for the continuation of the talks,” Kremlin spokesman Dmitry Peskov said, five weeks after Moscow began sending upwards of 150,000 of its own troops across Ukraine’s border.

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Meanwhile, Russia continued withdrawing some of its ground forces from areas around Kyiv. This comes after saying that it would reduce military activity near the Ukrainian capital and the northern city of Chernihiv.

“They are mining the whole territory. They are mining homes, mining equipment, even the bodies of people who were killed,” Zelensky said in his nightly video address to the nation.

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He urged residents to wait to resume their normal lives until they are assured that the mines have been cleared and the danger of shelling has passed.