The Kremlin denied that Russian troops were storming the Azovstal steel plant in Ukraine's southern port city of Mariupol, where Ukrainian fighters and civilians are trapped, and said humanitarian corridors were operating there on Thursday.

Asked if a claim by a senior Ukrainian official that Russian troops had broken into the plant's territory was true, Kremlin spokesman Dmitry Peskov referred reporters to President Vladimir Putin's previous order not to storm the plant.

Putin called off plans for an assault on the plant last month, telling his defence minister to seal it off instead.

(Reporting by Reuters)