Ukrainian President Volodymyr Zelensky has accused Russia of kidnapping the mayor of the southern port city of Melitopol, equating it to the actions of so-called Islamic State “terrorists”.

“They have transitioned into a new stage of terror, in which they try to physically liquidate representatives of Ukraine’s lawful local authorities,” Mr Zelensky said in a video address.

Kirill Timoshenko, the deputy head of Ukraine’s presidential office, posted a video on social media site Telegram which he said showed a group of armed men carrying mayor Ivan Fedorov across a square.

The prosecutor’s office of the Luhansk People’s Republic, a Moscow-backed rebel region in eastern Ukraine, said on its website that there was a criminal case against Mr Fedorov.

(PA Graphics)

The office accused him of “terrorist activities” and of financing the nationalist militia Right Sector to “commit terrorist crimes against Donbass civilians”. The office said it was looking for Mr Fedorov and called for anyone with information about his whereabouts to contact them.

An aide to Mr Zelensky later posted video of a protest demanding his release, which officials said drew 2,000 people on to the streets.

Meanwhile, authorities warned of a humanitarian catastrophe in the port city of Mariupol, which has been encircled by Russian forces and cut off from deliveries of food and medicine.

An explosion is seen in an apartment building after Russian’s army tank fires in Mariupol, Ukraine
An explosion is seen in an apartment building after it was hit by fire from a Russian army tank in Mariupol, Ukraine (Evgeniy Maloletka/AP)

Mariupol officials said on Friday that 1,582 people had been killed in the 12 days since the siege began.

“There is a humanitarian catastrophe in the city and the dead aren’t even being buried,” Mariupol’s mayor’s office said in a statement calling for Russian forces to lift the siege.

Ukrainian authorities have accused Russian forces of shelling evacuation routes and preventing civilians from escaping the city of 430,000 people.