Ukraine defiant as key port Mariupol teeters on brink

Ukrainian soldiers resisted a Russian ultimatum to lay down arms on Sunday in the pulverised port of MariupolUkrainian Prime Minister Denys Shmyhal said troops in Mariupol were still fighting despite a Russian demand to surrender by dawn

Kharkiv has been under heavy bombardment throughout the weekend (Felipe Dana/AP)

Sami Quadri, Adam Schreck and Mstyslav Chernov

Ukrainian Foreign Minister Dmytro Kuleba said there had not been any recent diplomatic communications between Russia and Ukraine at the level of their foreign ministries and that the situation in the port of Mariupol, which he described as "dire", may be a "red line" in the path of negotiations.