ICRC warns Mariupol facing 'worst-case scenario'

Ukraine's besieged port city of Mariupol faces "a worst-case scenario" if the warring parties don't urgently reach a "concrete humanitarian agreement", the International Committee of the Red Cross (ICRC) warned on Sunday.

"The ICRC stands ready to act as a neutral intermediary to facilitate dialogue on such humanitarian issues," it said in a statement.

The Azov Sea port city of around half a million has been under siege since early this month.

More than 2,100 residents have been killed since hostilities began, the local authorities said Sunday.

Ukraine and aid agencies say Mariupol faces a "humanitarian catastrophe", lacking water or heating and running out of food. 

"Time is running out for the hundreds of thousands trapped by the fighting," the ICRC said.

"History will look back at what is now happening in Mariupol with horror if no agreement is reached by the sides as quickly as possible."

ICRC president Peter Maurer called, in the statement, on all parties involved in the fighting to "place humanitarian imperatives first".

The ICRC said that people in Mariupol, including its own staff, were "sheltering in unheated basements, risking their lives to make short runs outside for food and water".

It added that "a concrete, precise, actionable agreement" was needed without delay so civilians wanting to leave can reach safety, and life-saving aid can reach those who stay.