President Volodymyr Zelensky has visited the city of Kherson days after it was liberated by Ukrainian troops.
He spoke to soldiers, saying Ukraine is "moving forward" and ready for peace.
The loss of Kherson, taken in the early stages of the invasion, was a major setback for Russia - though Moscow insists it remains Russian territory.
Russia had declared it the administrative centre of the illegally-annexed Kherson region, and it was the only regional capital to be occupied.
Kherson was captured in March, weeks after the invasion began. The region was then one of four to be illegally annexed after self-styled referendums were held in September.
The president also addressed a crowd in the city's main square, some of whom waved Ukrainian flags or wore them draped across their shoulders.
Asked where Ukrainian forces might advance next, he said: "Not Moscow... We're not interested in the territories of another country."
The president also joked he had come to Kherson because he "wanted a watermelon" - in reference to the locally-grown fruit which has become a popular Ukrainian symbol of resistance.
In response to Mr Zelensky's visit, the Kremlin said that Kherson was part of Russia.
"We leave this without comment," Kremlin spokesman Dmitry Peskov said, adding: "You know, this territory is part of the Russian Federation."
Mr Zelensky had previously said that investigators have uncovered more than 400 war crimes in areas of Kherson abandoned by Russian forces as they retreated.
At a ceremony in Moscow, Russian President Vladimir Putin said the annexation of Luhansk, Donetsk, Zaporizhzhia and Kherson was "non-negotiable".
But in the following weeks Ukraine began to make gains in the south of the country, advancing towards Kherson and putting Russian forces under increasing pressure.
Finally, Russian forces withdrew and Ukrainian troops entered the city on Friday.
Locals were seen celebrating, some reuniting with loved ones they had not seen for months. The mood in the city was one of jubilation and relief, but also trepidation the BBC's Jeremy Bowen reported.
During his visit on Monday, Mr Zelensky sang the Ukrainian national anthem as the country's flag was hoisted above the main administrative building.
He told troops that Ukraine is "ready for peace, peace for all our country," the Reuters news agency reported.
He thanked Nato and other allies for their support, adding that high mobility artillery rocket systems (Himars) from the United States had made a big difference.
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