Fleeing Ukrainian families describe the “hell” they left behind in the besieged city of Mariupol, of seeing corpses in the streets and of sleeping in sub-zero temperatures, hiding in cellars. Shelled relentlessly by Russian forces, they said they were forced to melt snow for drinking water and cook food scraps on open fires with food, water and power supplies cut off. “They fire so many rockets,” Tamara Kavunenko, 58, told AFP, one of more than 4,300 Mariupol residents who escaped to Ukraine’s central city of Zaporizhzhia this week. “In the streets there are the bodies of many dead civilians,”…