Ukrainian President Volodymyr Zelensky said on Wednesday his country stands ready for any format of prisoner exchange with Russia to free people from the besieged city of Mariupol, the Interfax-Ukraine news agency reported.

"We are ready for any format of exchange for the sake of our people, both military and civilian," Zelensky said during a joint briefing with European Council President Charles Michel in Kiev.

Currently, some 120,000 civilians remain in Mariupol, Zelensky said, noting that the humanitarian situation in the city is deteriorating.

Earlier in the day, Ukrainian Deputy Prime Minister Iryna Vereshchuk said that Ukraine and Russia have reached a preliminary agreement on establishing a humanitarian corridor to evacuate women, children and the elderly from the embattled city.

Mariupol, a key Azov Sea port city in eastern Ukraine, saw one of the worst violence in the Russia-Ukraine conflict.