The mayor of southern Ukraine's Melitopol was kidnapped on Friday by Russian soldiers occupying the city, President Volodymyr Zelensky and Ukrainian officials said.
"A group of 10 occupiers kidnapped the mayor of Melitopol Ivan Fedorov," Ukraine's parliament said on Twitter.
"He refused to cooperate with the enemy," it added.
It said the mayor was seized when he was at the city's crisis centre dealing with supply issues.
In a video message late Friday, Zelensky confirmed the abduction, calling Fedorov "a mayor who bravely defends Ukraine and the members of his community".
"This is obviously a sign of weakness of the invaders... They have moved to a new stage of terror in which they are trying to physically eliminate representatives of legitimate local Ukrainian authorities," he said.
"The capture of the mayor of Melitopol is therefore a crime, not only against a particular person, against a particular community, and not only against Ukraine. It is a crime against democracy itself... The acts of the Russian invaders will be regarded like those of Islamic State terrorists," he said.
The deputy head of Ukraine's presidential administration, Kirillo Timoshenko, previously posted a video on Telegram showing soldiers coming out of a building holding a man dressed in black, his head apparently covered with a black bag.
According to the Ukrainian parliament, another regional official, the deputy head of the regional council of Zaporizhzhia -- 120 kilometres (75 miles) north of Melitopol -- was abducted and then released a few days ago.
Before the Russian invasion, Melitopol had just over 150,000 inhabitants.
