Ukrainian minister Iryna Vereshchuk said about 100,000 civilians remained trapped in the city, which has suffered weeks of bombardment from Russian forces.
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Russian forces on Thursday confiscated 14 tons of humanitarian aid from buses bound for Melitopol in southern Ukraine, according to Vereshchuk, the Ukrainian minister of reintegration of temporarily occupied territories. Vereshchuk said the food and medication was loaded on 12 buses.
Russian forces also blocked 45 buses going to Berdiansk on Thursday en route to Mariupol, she added.
"We are negotiating for the buses to be returned and for the Melitopol residents tomorrow to evacuate using these buses," she said.