Video posted by Ukraine's Azov Battalion on social media showed a powerful explosion destroying a high-rise building in the southeastern city of Mariupol on Monday. The drone footage shared by the special forces unit, which includes members of a far-right political group, also showed fires blazing and thick, dark plumes of smoke rising from several buildings in the port city. Mariupol, which sits on the Azov Sea, is surrounded by Russian forces and has come under heavy bombardment recently. It has been cut off from food supplies, water, electricity and heat for more than a week, despite earlier talks on creating aid or evacuation convoys. Since launching its invasion of Ukraine on Feb. 24, Moscow has waged a multi-pronged attack and encircled several cities. The fight for the southern city of Mariupol is crucial because its capture could help Russia establish a land corridor to Crimea, which it seized from Ukraine in 2014.