A Red Cross team on its way to Mariupol, Ukraine to facilitate the safe passage of some 100,000 civilians had to backtrack after arrangements and conditions made it impossible to proceed, said the humanitarian group on Friday.

"The International Committee of the Red Cross team, which consists of three vehicles and nine personnel, did not reach Mariupol or facilitate the safe passage of civilians today," the ICRC said.

"They will try again on Saturday to facilitate the safe passage of civilians from Mariupol."

For the operation to succeed, it is critical that the Ukrainian and Russian sides respect the agreements and provide the necessary conditions and security guarantees, said the ICRC.

"If and when the safe passage operation does happen, the ICRC's role as a neutral intermediary would be to accompany the convoy out from Mariupol to another city in Ukraine," said the Red Cross.

Mariupol Mayor Vadym Boychenko said on Monday that up to 160,000 civilians are stranded in the port city, which has been besieged for weeks.

A spokesman earlier said the Red Cross is in communication with Ukrainians and Russians on final details of how tens of thousands of civilians stranded in Mariupol will be evacuated.

Humanitarian groups have been unable to reach Mariupol since Russian forces began bombing the city.

"The parties to the conflict would also need to fulfill the agreements reached to allow for this operation to happen," said spokesman Ewan Watson.

He said if it happens, then the Red Cross' role as a "mutual intermediary" will lead a convoy out of Mariupol to another city in Ukraine.

So far, 54 buses are reported to be in the convoy, which could take tens of thousands of civilians away from the city.

"We are running out of adjectives to describe the horrors that residents in Mariupol have suffered. The situation is horrendous and deteriorating," he said.

Watson said allowing people to leave and letting aid supplies in is now a humanitarian imperative.

"The people of Mariupol have suffered weeks of heavy fighting with dwindling water, food, and medical supplies. Piecing together the safe passage convoy has been and remains extremely complex."

According to some reports, Russian troops forced Ukrainian civilians to relocate to areas under their control. (Anadolu Agency)

•PHOTO: A refugee camp is set up in Bezymyenny outside the Ukrainian city of Mariupol under the control of Russian military and pro-Russian separatists, on March 25, 2022. (Stringer - Anadolu Agency)

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