Ukrainian President Volodymyr Zelensky said Kyiv's forces were swiftly recapturing more territory, especially in the south while Moscow's military leadership faced rare public backlash from within Russia over its handling of the war.
Mr. Zelensky said in a video address on Thursday that Kyiv's forces recaptured more than 500 sq. km of territory and dozens of settlements in the southern Kherson region alone in October.
"There are successes in the east as well. The day will surely come when we will report on successes in the Zaporizhzhia region (in southeastern Ukraine) as well, in those areas that the occupiers still control," Mr. Zelensky said.
Reuters could not independently verify battlefield accounts.
Russian President Vladimir Putin marks his 70th birthday on Friday as the invasion of Ukraine has begun to unravel after a Ukrainian counteroffensive in which thousands of sq. km of territory have been retaken since the start of September.
Thousands of Russian troops have retreated after the front line 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 the Kherson region, slammed "generals and ministers" in Moscow for failing 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 TV hosts.
"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 (the Ukrainians) have hugely increased their amount of weapons... But what have you done in that time?"
Ukrainian military analyst Oleh Zhdanov said there were several factors for Kyiv's recent rapid gains including Western military aid and tactical mistakes by the Russian army.
"On the Kharkiv front, we are advancing in a broad sweep," he told Ukrainian Apostrophe TV. "On the southern front ... the aim is to trap and push Russian forces either onto the West bank of the Dnipro (river) or back to the city of Kherson."
In the northeastern Kharkiv region where Ukrainian forces regained a large swathe of ground in September, the bodies of 534 civilians including 19 children were found after Russian troops left, Serhiy Bolvinov of the National Police in Kharkiv told a briefing posted online.
The total included 447 bodies found in Izium. He also said that investigators had found evidence of 22 sites being used as "torture rooms". There was no immediate comment from Russia.
On Thursday, the regional governor said a missile demolished an apartment block and killed seven persons in the city of Zaporizhzhia in the southern region of the same name, which Moscow says it has annexed.
The strike left some people buried under rubble and at least five people were missing.
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, Mr. Zelensky accused Russia of deliberately targeting the same spot twice in succession.
"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."
Moscow says it does not deliberately target civilians.
In remarks to Australia's Lowy Institute, Mr. Zelensky said NATO should launch preventive strikes on Russia to preclude its use of nuclear weapons. Kremlin spokesman Dmitry Peskov denounced the comments as "an appeal to start yet another world war with unpredictable, monstrous consequences," according to RIA news agency.
The Zaporizhzhia missile attack came a day after Mr. Putin signed a law to incorporate four partially occupied Ukrainian regions into Russia, including Zaporizhzhia, in Europe's biggest attempted annexation since World War Two.
Kyiv called the new law the act of a "collective madhouse".
Russia moved to annex the regions after holding what it called referendums – votes denounced by Kyiv and Western governments as illegal and coercive.
Separately, Sweden's security service said an underwater crime scene investigation of the energy pipelines linking Russia and Germany via the Baltic Sea found evidence of detonations and strengthened suspicions of sabotage.
