Russian forces occupied Ukraine's northern Slavutych city, according to its mayor on Saturday.
Yuriy Fomichev said in a video message that city officials received a warning from Russian forces three days ago to surrender without a fight.
Noting they defended the city resolutely despite the warning, Fomichev said: "But Slavutych is under occupation as of today."
Fomichev said he is negotiating with Russian troops for the evacuation of residents.
The mayor was kidnapped earlier by Russian forces after a group of protestors refused to disperse. He was later released.
When Russian forces captured the city hospital, residents took to the streets in protest, unfurling a large Ukrainian flag and shouting slogans against Russia, said Aleksander Pavlyuk, head of the Kyiv Regional Military Administration.
Russian forces threw sonic charges to disperse the crowd and opened fire into the air, he said.
Images of demonstrations in Slavutych and Russians opening fire on civilians were also shared on social media.
The city was built especially for personnel who evacuated the 1986 Chernobyl Nuclear Power Plant disaster.
The Russia-Ukraine war, which began Feb. 24, has met international outrage, with the EU, US and UK, among others, implementing tough financial sanctions on Moscow.
At least 1,081 civilians have been killed in Ukraine and 1,707 injured, according to UN estimates, while noting that the true figure is likely far higher.
More than 3.7 million Ukrainians have also fled to neighboring countries, including over 2 million to Poland, with millions more displaced inside Ukraine, according to the UN refugee agency.
