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Moscow on Monday accused Kyiv of preventing civilians trapped with Ukrainian soldiers in Mariupol's Azovstal steelworks from leaving the besieged industrial centre, despite a ceasefire announcement.
The Russian Defence Ministry had said it would allow civilians to leave Mariupol's sprawling steel plant, which has been sheltering the remaining Ukrainian resistance in the south-eastern port city.
But the Russian army on Monday evening said no one used the humanitarian corridor.
"The Kyiv authorities have again cynically undermined this humanitarian operation," it said, accusing the Ukrainian government of "indifference" towards its citizens.
The ministry had said its troops would stop hostilities from 2pm Moscow time on April 25 and withdraw to a safe distance to ensure free, safe passage for civilians.
It said the women, children and Azovstal staff would be taken "in any direction they have chosen".
The ministry said the Ukrainian side should show "readiness" to start the humanitarian evacuation "by raising white flags".
It said this information would be communicated to those inside Azovstal "via radio channels" every 30 minutes.
Russia last week said it had gained full control of the strategic eastern Ukrainian city, except for the huge industrial area.
Russian President Vladimir Putin ordered a blockade of the steel works, where hundreds of civilians are reportedly sheltering with Ukrainian troops.