In recent days, Russia has ordered civilians out of Kherson in anticipation of a Ukrainian assault to recapture the city, the only regional capital Moscow has seized since its invasion in February.
Kherson, with a prewar population of almost 300,000, has been left cold and dark after power and water were cut to the surrounding area in the past 48 hours, both sides said.
Russian-installed officials blamed Ukrainian "sabotage" and said they were working to restore electricity.
Ukrainian officials said the Russians had dismantled 1.5 km of power lines, and electricity probably would not return until Ukrainian forces recapture the area.
Ukraine has described the evacuation of the area as a forced deportation, a war crime.
Russia says it is sending residents away for safety.
Kherson lies in the only pocket of Russian-held territory on the west bank of the Dnipro River that bisects Ukraine.
Recapturing it has been the main focus of Ukraine's counter-offensive in the south, which has accelerated since the start of October.
Ukrainian forces on the nearby frontline have told Reuters they expect a bitter fight against Russian troops determined to exact a blood price before being forced out.
Ukraine's military said Russian forces "disguised in civilian clothes, occupy the premises of civilians and strengthen positions inside for conducting street battles".
Russian forces were "involved in looting and theft from residents and from infrastructure sites and are taking away equipment, food and vehicles to the Russian Federation", it said in an update late on Monday.
Reuters was seeking comment from Russian authorities on the Ukrainian allegations. Moscow denies abusing civilians.
Ukrainian President Volodymyr Zelenskiy said on Monday the Donetsk region in the east remained the "epicentre" of fighting, with hundreds of Russians killed every day.
The towns of Bakhmut and Avdiivka are the focal points of the heaviest fighting in Donetsk region.
On the diplomatic front, White House national security adviser Jake Sullivan is engaging in confidential talks with senior Russian officials aimed at lowering the risk of a broader war over Ukraine, a source familiar with the conversations said on Monday.
The source said the talks had been taking place in recent months and are ongoing.
The Kremlin refused to comment on the talks, first reported by the Wall Street Journal.
The war has inflicted major damage on the global economy and raised fears of nuclear conflict.
"We reserve the right to speak directly at senior levels about issues of concern to the United States," White House press secretary Karine Jean-Pierre said at the White House briefing, adding the conversations have focused "only on risk reduction".
US' support for Ukraine will be "unflinching and unwavering" regardless of the outcome of Tuesday's congressional elections, she said.
Ukrainian presidential adviser Mykhailo Podolyak said Ukraine was ready to negotiate an end to the war with a future Russian leader but not with Vladimir Putin, after a Washington Post report the US had urged Kyiv to signal a readiness for peace talks to ensure it retains Western support.
"Ukraine has never refused to negotiate. Our negotiating position is known and open," Podolyak said on Twitter, adding that Russia should first withdraw forces from Ukraine.
"Is Putin ready? Obviously not."
Zelenskiy in his nightly address on Monday said it was vital to oblige Russia to participate in "genuine" peace talks, describing the country as a destabilising force on a range of issues, including climate change.
