
Ukraine's Azov regiment has posted a video showing women and children supposedly sheltering underground at the Azovstal plant - the last part of Mariupol that is not under Russian control.
Women and children in a crowded room can be heard saying they are running out of food and water and praying to evacuate from the southern city.
Some say they haven't seen daylight in weeks, having been there since February. It is believed to have been filmed on April 21.
On the same day, President Vladimir Putin called off a planned Russian attack on the steel plant and ordered his troops to keep him surrounded.
Moscow also stated that it had full control of the strategic city, a claim denied by Ukraine, which says Russian troops have not yet taken the Azovstal steel plant.
The factory, a maze of tunnels and workshops, is a major industrial site in central Mariupol.
The takeover of the Sea of Azov port, which has almost been flattened by weeks of heavy Russian bombing is a key goal of the Kremlin's war and paves the way for Russian troops to join an ongoing Russian offensive in the eastern donbass region.