At least 100 civilians remain in a steel works that is under heavy Russian fire in the southern Ukrainian city of Mariupol, an aide to the city's mayor said on Tuesday.

"In addition to the military, at least 100 civilians remain in the (Azovstal) shelters. However, this does not reduce the density of attacks by the occupiers," mayoral aide Petro Andryushchenko wrote on the Telegram messaging app.

(Reporting by Natalia Zinets, Editing by Timothy Heritage)