Russia unleashed rockets on Tuesday on an encircled steelworks in Mariupol, Ukraine's last redoubt in the port city, after a ceasefire broke down with some civilians still trapped beneath the sprawling site despite a U.N.-brokered evacuation.

However, scores of evacuees who managed to leave under U.N. and Red Cross auspices at the weekend after cowering for weeks under the Azovstal plant finally reached the relative safety of Ukraine-controlled Zaporizhzhia.

"We would have hoped that many more people would have been able to join the convoy and get out of hell. That is why we have mixed feelings," Pascal Hundt from the International Committee of the Red Cross (ICRC) told journalists.