Ukrainian President Volodymyr Zelensky has accused Russian soldiers of committing war crimes and killing civilians in Kherson, parts of which were retaken by Ukraine's army last week after Russia pulled out.
"Investigators have already documented more than 400 Russian war crimes. Bodies of dead civilians and servicemen have been found," Zelensky said in his nightly video address on Sunday.
"The Russian army left behind the same savagery it did in other regions of the country it entered," he said.
Reuters was unable to verify his allegations. Russia denies its troops intentionally target civilians.
War crimes uncovered after Russians pulled out: Zelensky
Kherson residents recount abuse by Russian forces
Demining of Kherson and power restoration underway
Fighting rages in eastern Donetsk and Luhansk regions
Mass graves have been found in several places across Ukraine since the start of the invasion on Feb 24, including civilian bodies showing evidence of torture discovered in the Kharkiv region and in Bucha, near Kyiv. Ukraine has accused Russian troops of committing crimes.
A United Nations commission in October said war crimes were committed in Ukraine and that Russian forces were responsible for the "vast majority" of human rights violations in the early weeks of the war.
Ukrainian troops arrived in the centre of southern Kherson region on Friday after Russia abandoned the only regional capital it had captured since Moscow launched its invasion.
Villagers holding flowers waited on the road to Kherson to greet Ukrainian soldiers on Saturday as they poured in to secure control of the right bank of the Dnipro River.
This marks Moscow's third major retreat of the war and the first to involve yielding such a large occupied city in the face of a major Ukrainian counter-offensive using US supplied High Mobility Artillery Rocket System (HIMARS).
The United States on Monday will announce new sanctions on a transnational network of individuals and companies that have been working to procure military technologies for Russia's war in Ukraine, US Treasury Secretary Janet Yellen said.
Yellen told reporters on the sidelines of the G20 summit in Bali the sanctions would target 14 individuals and 28 entities, including financial facilitators, but she declined to provide details on where they were located.
Russia has managed to procure drones from Iran that have been used to attack cities and power infrastructure in Ukraine.
Artillery exchanges echoing over Kherson on Sunday failed to discourage crowds of jubilant, flag-waving residents bundled up against the cold from gathering on the city's main square.
"We are happy now, but all of us are afraid of the bombing from the left bank," said Yana Smyrnova, 35, a singer, referring to Russian guns on the east side of the Dnipro River that runs close to the city.
The Ukraine Armed Forces' southern command said on Monday that Russian forces continued to "inflict fire damage on our troops and de-occupied settlements along the right bank of the Dnipro".
The governor of Kherson region, Yaroslav Yanushevych, said the authorities had decided to maintain a curfew from 5 pm to 8 am and ban people from leaving or entering the city as a security measure.
"The enemy mined all critical infrastructure," Yanushevych told Ukrainian TV. "We are trying to meet within a few days and (then) open the city," he said.
In an online post Yanushevych warned people about reports of humanitarian aid arriving in Kherson's Freedom Square and urged people to steer clear of the centre of the city as demining operations were due to proceed there.
Zelensky also warned Kherson residents about the presence of Russian mines. "I am asking you please not to forget that the situation in Kherson region remains very dangerous," he said.
Residents said the Russians had pulled out gradually over the past two weeks, but their final departure became clear only when the first Ukrainian troops entered Kherson on Thursday.
"It was a gradual thing," said Alexii Sandakov, 44, a videographer. "First their special police went. Then the ordinary police and their administration. Then you started seeing fewer soldiers in the supermarkets and then their military vehicles driving away."
Many residents interviewed by Reuters said they tried to minimise their contact with the Russians and knew of people who were arrested and abused for showing any expression of Ukrainian patriotism.
Sandakov said Russian troops had looted the homes of Ukrainian soldiers who left the city before the takeover and would inspect the bodies of young men passing through checkpoints for tattoos of Ukrainian nationalist groups.
Russia has denied abuses against civilians or attacks on civilians since the war began.
Ukraine's defence ministry said it had recaptured 179 settlements and 4,500 square kilometres (1,700 square miles) along the Dnipro River since the beginning of the week.
Ukrainian armed forces' general staff reported fierce fighting along the eastern front in the Donetsk and Luhansk regions.
"The enemy does not stop shelling settlements and the positions of our units along the front line ... It continues to strike critical infrastructure and civilian homes," the general staff said on Monday.
It said that in the past 24 hours, Russian forces launched four missile and 13 air strikes, as well as about 60 attacks from rocket salvo systems.
In reply, Ukrainian forces attacked Russian positions 16 times, destroying or damaging 10 areas containing personnel, weapons and military equipment, it said.