A convoy of buses set out for the besieged southern Ukrainian city of Mariupol on Thursday to try to deliver humanitarian supplies and bring out civilians, Deputy Prime Minister Iryna Vereshchuk and the Red Cross said.
Vereshchuk said 45 buses were on their way to Mariupol after the International Committee of the Red Cross (ICRC) confirmed Russia had agreed to open a safe corridor.
In Geneva, the ICRC said its convoy was on the way to the port city, but called on both sides to agree the exact terms for the safe passage of civilians. By nightfall it said that its two trucks had arrived in the city of Zaporizhzhia with aid items and medical supplies.
"For logistics and security reasons, we'll be ready to lead the safe passage operation tomorrow, Friday, provided all the parties agree to the exact terms, including the route, the start time and the duration," ICRC spokesperson Ewan Watson said.
"It's desperately important that this operation takes place. The lives of tens of thousands of people in Mariupol depend on it," he said.
In its day-end update, the ICRC said that "militaries on the ground need to give civilians and humanitarian organisations security guarantees and practical agreements to allow aid in and for those who wish to evacuate safely".
To date in the five-week-old conflict, the ICRC has led two evacuations of civilians from the northeastern city of Sumy.
The United Nations has been unable to secure access to Mariupol, Kherson and Volnovakha as the safety of aid convoys and civilians could not be assured, U.N. spokesperson Jens Laerke said.
"Nevertheless, should this latest reported commitment from the parties succeed in delivering a period during which civilians can move, we will do all we can to support those who are fleeing the violence or remain and need urgent assistance," he said in a statement to Reuters.
The Mariupol mayor said this week that up to 170,000 residents were trapped there with no power and dwindling supplies.
"There are 45 buses en route to Mariupol," Vereshchuk said in a statement on Thursday.
The city, which usually has a population of more than 400,000, has been a strategic focus of Russia's invasion of Ukraine and has suffered near-constant bombardment.
Repeated attempts to organise safe corridors have failed, with each side blaming the other. Russia denies attacking civilians in its assault on Ukraine that began on Feb. 24.
(Reporting by Pavel Polityuk in Lviv and Stephanie Nebehay in Geneva; Editing by Timothy Heritage and Alistair Bell)