Russian President Vladimir Putin proclaimed the effort by Russian forces to capture Mariupol a "success," but ordered Russian forces to halt outside the city's besieged Azovstal steel factory and blockade it "so that a fly can't get through."
In a meeting with Russian Defense Minister Sergei Shoigu, Putin said: "Completing the military task of liberating Mariupol is a great achievement, I congratulate you."
Ukrainian forces still hold the Azovstal plant in the southeastern port city and Shoigu told Putin that Russian forces would need three or four days to take over the factory.
Putin then said the Russian forces "must think ... about preserving the life and health of our soldiers and officers," adding:
There is no need to climb into these catacombs and crawl underground through these industrial facilities. Block off this industrial area so a fly cannot get through."
"Yes sir," Shoigu replied.
Putin said that Russia would offer the Ukrainian defenders still in the plant to lay down arms.
"The Russian side guarantees their lives and decent treatment in accordance with the relevant international legal acts," he said. "All those who are injured will receive qualified medical assistance."
Ukrainian commanders on the ground have said Russian forces have not honored agreements to open humanitarian corridors or enforce ceasefires and have continued to bombard the city.
The port city has been nearly completely destroyed by weeks of Russian bombardment, and tens of thousands of civilians still await evacuation, according to Ukrainian officials.
In a statement on Thursday, Ukrainian Deputy Prime Minister Iryna Vereshchuk urged the Russian side to open an evacuation corridor from Azovstal. "There are about 1,000 civilians and 500 wounded servicemen there now," she said.
"They all need to be evacuated out of Azovstal today! I call on world leaders and the international community to focus their efforts on Azovstal now. It is a key point and a key moment for the humanitarian efforts now!"