A Red Cross convoy will try again to evacuate civilians from the besieged port of Mariupol on Saturday as Russian forces looked to be regrouping for new attacks in southeast Ukraine.

Encircled since the early days of Russia's five-week old invasion, Mariupol has been Moscow's main target in Ukraine's southeastern region of Donbas. Tens of thousands are trapped there with scant access to food and water.

The International Committee of the Red Cross (ICRC) sent a team on Friday to lead a convoy of about 54 Ukrainian buses and other private vehicles out of the city, but they turned back, saying conditions made it impossible to proceed.