Ukraine on Monday rejected outright a Russian call to lay down arms and surrender the besieged city of Mariupol, where fierce fighting has trapped an estimated 300,000 people with dwindling supplies. “There can be no talk of any surrender, laying down of arms,” Ukrainian Deputy Prime Minister Iryna Vereshchuk told Ukrainska Pravda. “We have already informed the Russian side about this.” Russia’s proposal was offered Sunday by Gen. Mikhail Mizintsev, who said a “terrible humanitarian catastrophe” was unfolding in Mariupol. The strategic port city has faced particularly heavy bombardment by Russian forces in the three weeks since the invasion began, with authorities saying that roughly 2,500 people have been killed there, though the true number may be much higher. Gen. Mizintsev’s Sunday overture included the promise that civilians and disarmed defenders would be allowed safe passage out of the strategic port city. The plan also outlined the opening of humanitarian corridors by which food, medicine, and other kinds of aid could have been brought in. Vereshchuk said that more than 3,000 people were able to leave Mariupol on Sunday, with government plans in place to send a fleet of buses there on Monday for further evacuations, according to Reuters.