Russia will not "subdue" the captured city of Slavutych, a defiant Ukrainian President Volodymyr Zelensky said Saturday.
Russian forces that entered the city are encountering the same spirit of resistance evident in other parts of the country, the president said in a video posted to social media.
"Free Slavutych which the invaders cannot subdue," he said.
Earlier Saturday, hundreds of locals amassed in the city square in a protest following the arrival of Russian troops.
Images and video geolocated by CNN showed a crowd of about several hundred people.
"Slavutych is Ukraine!" they chanted in the main square. "Glory to Ukraine."
Zelensky said every "demonstration of our resistance ... proves that Ukraine is a country full of life."
Russian forces briefly detained the city's mayor but eventually released him, according to a statement from Ukrainian political party Sluha Narodu.
The UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), condemned Russia's seizure of the city, which was built to house workers of the nearby Chornobyl nuclear power plant.
The IAEA said in a statement it was closely monitoring the situation. The agency's director general, Rafael Mariano Grossi, voiced concerns about the ability of power plant staff to return safely to their homes.
Some background: The arrival of Russian forces in Slavutych came after several days of shelling against the city, which is strategically located close to the Dnieper River, about 95 miles (150 kilometers) north of Kyiv and close to the border with Belarus.
According to local officials, the city has been isolated almost since the beginning of the Russian invasion.