(Reuters) - Ukraine's deputy prime minister said on Wednesday that an agreed humanitarian corridor to evacuate civilians from the Azovstal steelworks in Mariupol had not worked as planned, blaming Russian forces for not holding their ceasefire.

       Deputy Prime Minister Iryna Vereshchuk also said Russian-organised buses failed to deliver evacuees on time to the point where Ukrainian buses and ambulances were waiting.

       Ukrainian officials estimated that about 1,000 civilians were sheltering underneath the vast Azovstal steel plant, which is the last Ukrainian stronghold in the southeastern port city of Mariupol.

       (Reporting by Max Hunder; Editing by Chris Reese)