Reuters could not independently verify battlefield accounts.
Ukrainian forces have regain control of thousands of square kilometres (miles) of territory since the beginning of September as the Russian front line has crumbled, first in the northeast, and, since the beginning of this week, also in the south.
In rare but growing public criticism of Russia's top military officials, Kirill Stremousov, the deputy head of the Russian-backed administration in Kherson region, said the "generals and ministers" in Moscow failed to understand the problems on the front lines.
There was no immediate comment from Russia's defence ministry.
Discontent has begun to bubble up among even loyalist state television commentators.
"Please explain to me what the general staff's genius idea is now?" Vladimir Solovyov, one of the most prominent Russian talk show hosts, said on his livestream channel.
"Do you think time is on our side? They have hugely increased their amount of weapons," he said of Ukrainian forces.
"But what have you done in that time?"
'ADVANCING IN BROAD SWEEP'
In the northeastern Kharkiv region where Ukrainian forces regained a large swathe of territory in September, the bodies of 534 civilians including 19 children were found after Russian troops left, police official Serhiy Bolvinov told a briefing.
The total included 447 bodies found in Izium. He also said that investigators had found evidence of 22 "torture rooms". There was no immediate comment from Russia.
On Thursday, a regional governor said a missile demolished an apartment block and killed seven people in the city of Zaporizhzhia in the southern region of the same name, which Russia says it has annexed.
Eduard, a 49-year-old man who survived the attack, said he was woken at around 5 a.m. by a strong explosion. "The room filled with smoke and dust. I jumped up to go see what had happened," he said.
In an online address to new security and energy co-operation forum the European Political Community, Zelenskiy accused Russia of targeting the same spot twice to kill responders.
"In Zaporizhzhia, after the first rocket strike today, when people came to pick apart the rubble, Russia conducted a second rocket strike. Absolute vileness, absolute evil."
Russia says it does not deliberately target civilians.