Ukrainian President Volodymyr Zelenskyy accused Russia of committing war crimes and killing civilians in Kherson as he visited the newly recaptured southern city on Monday.

The key eastern city is the biggest prize yet won by Ukrainian forces after Russian forces decided to pull out of the region last week.

"We are moving forward," he told troops standing in formation in front of the administration building in the city's main square, where parents had also turned out with children, some pushing baby strollers, some waving Ukrainian flags or draped in them. "We are ready for peace, peace for all our country."

Zelenskyy thanked NATO and other allies for their ongoing support in the war against Russia and said the delivery of rockets from the United States had made a big difference for Kyiv.

"I'm really happy, you can tell by the reaction of the people, their reaction is not staged," the president said.

Minutes before he arrived, nearby shelling could be heard from the center of Kherson, and after he finished speaking several more blasts of artillery echoed over the city.

Kherson residents have greeted arriving Ukrainian troops with joy since Friday, when Russia abandoned the only regional capital it had captured since Moscow launched its invasion.

In an overnight televised address, Zelenskyy said investigators had already documented more than 400 war crimes committed by Russia during its eight-month occupation.

"Bodies of dead civilians and servicemen have been found," he said. "The Russian army left behind the same savagery it did in other regions of the country it entered."

Reuters has spoken to residents in formerly occupied parts of the Kherson region in recent days who have described killings and abductions of civilians but has not verified such reports independently.

Russia denies its troops intentionally target civilians or have committed atrocities in occupied areas. Mass burial sites have been found in several other parts of Ukraine previously occupied by Russian troops, including some with civilian bodies showing signs of torture, which Kyiv blames on Moscow.

'Invited into a cellar"

Residents interviewed by Reuters said they had tried to minimize contact with the Russians and knew of people who were arrested and abused for any discernable Ukrainian patriotism.

Russian soldiers "would approach you in the street and ask if you were Ukrainian or Russian. If you said Ukrainian, they would take you away," Natalia Papernaya, a 43-year-old clothing designer, said Sunday.

The Russians, she said, had arrested her friend for taking a photo of a neighbor's home to reassure the owners it had survived a nearby shell blast.

The troops had pulled her friend's hood over her eyes, taped it in place, put her in a cellar for a day and demanded to know for whom she was taking pictures.

"They didn't touch her," Papernaya said, but the friend heard the screams of other detainees and some who were forced to shout out praise for Russian President Vladimir Putin.

"There were many people in there, women and men," she said.

Yana Shaposhnikova, 36, another clothing designer, said she had buried her yellow and blue Ukrainian flag.

"If you wore anything yellow and blue you could be shot or invited into a cellar where you would be tortured," she said.

A volunteer she knew who was delivering humanitarian aid to outlying areas had been taken to an underground jail, deprived of sleep and interrogated for three days about whether she was reporting on Russian positions, she said.

Residents have described other abductions and killings to Reuters, including one account of a neighbor shot dead and three people carried off by troops in the village of Blahodatne north of Kherson.

It was not possible to verify the accounts.

Sanctions

Meanwhile, the United States was set to announce new sanctions Monday against 14 individuals and 28 entities that have worked to procure military technologies for Russia's war in Ukraine, U.S. Treasury Secretary Janet Yellen said.

Russia has managed to procure drones from Iran that have been used to attack cities and power infrastructure in Ukraine.

Russian President Vladimir Putin is not attending the summit, instead sending his foreign minister, Sergei Lavrov, who became subject to speculation about his health after reports he was taken to an Indonesian hospital.

Ukraine's recapture of Kherson marked Moscow's third major retreat of the war and the first to involve yielding such a large occupied city.

Russian forces who retreated across the Dnipro River continued to fire on Ukrainian troops and newly retaken settlements from new positions on the opposite bank, the Ukraine Armed Forces' southern command said Monday.

Regional Gov. Yaroslav Yanushevych said a curfew would be maintained from 5 p.m. to 8 a.m. and people would be banned from leaving or entering the city for a few days for security.

"The enemy mined all critical infrastructure," he said.

Zelenskyy also warned Kherson residents about Russian mines. "I am asking you please not to forget that the situation in Kherson region remains very dangerous," he said.

Ukraine's defence ministry said it had recaptured 179 settlements and 4,500 square kilometers (1,700 square miles) along the Dnipro River since the beginning of the week.

In eastern Ukraine, its forces have faced relentless Russian onslaughts. Ukraine's armed forces' general staff on Monday said fighting was fierce 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," it said.