The mayor of the eastern Ukrainian city of Mariupol has disputed Russian President Vladimir Putin's claims that his forces have "completed the combat effort to liberate" the city.

Vadym Boichenko said at an online news conference on Thursday that Mariupol has always been a city for Ukrainians, and stressed that fighters are still defending it.

Boichenko said about 100,000 civilians still remain in Mariupol, with 300 to 1,000 of them believed to be taking shelter in the Azovstal steel plant. The complex has served as one of the strongholds for the city's defenders.

An adviser to the mayor said on social media on Thursday that Russian forces have been continuing their attacks on the plant and elsewhere in the city.