Ukrainian President Volodymyr Zelenskyy has requested a prolonged ceasefire to evacuate further residents from the ravaged city of Mariupol in southern Ukraine as Russia increases its attack on the Azovstal steel complex, the final bastion of Ukrainian forces there.

Around 200 individuals, including children, are taking refuge in the enormous plant's underground bunkers, and Zelenskyy stated that it was essential to "maintain the silence" to evacuate them all.

"Simply lifting them out of those basements, out of those underground bunkers, will take time. We cannot utilize heavy equipment to clear the rubble in the current conditions. "Everything must be done manually," the president stated during Thursday's early morning speech to the nation.

Zelenskyy has once again appealed to the United Nations for aid following the evacuation of hundreds of people from Mariupol and other locations this week by the UN and Red Cross.

According to a Ukrainian MP, Russian forces are inside the Azovstal plant. The regiment commander stationed inside the sprawling facility described the situation as "extremely difficult" with his soldiers engaged in "heavy, bloody battles" with the Russians.

"I am proud of my soldiers for their superhuman efforts to contain the enemy's pressure," Lieutenant Colonel Denis Prokopenko stated in a brief video broadcast to Telegram.

Moscow has denied any assault on Azovstal and claims its forces will pause shooting for three days beginning Thursday to allow for the opening of a humanitarian corridor for civilians.

"On May 5, 6, and 7, the Russian armed forces will open a humanitarian corridor from the Azovstal metallurgical plant's territory to evacuate civilians from 8 a.m. to 6 p.m. (05:00 a.m. to 15:00 a.m. GMT)," the defense ministry stated on Wednesday.

Over 300 residents were evacuated from Mariupol and other southern Ukraine areas on Wednesday as part of a joint UN-Red Cross operation, according to the UN humanitarian coordinator for Ukraine, Osnat Lubrani.

"While this second evacuation of civilians from Mariupol and surrounding areas is significant, much more must be done to ensure that all civilians caught up in fighting can flee in the direction of their choice," Lubrani added.

It is unknown whether additional UN evacuations are being planned.

Zelenskyy stated during a phone chat with UN Secretary-General Antonio Guterres that UN assistance was required to assist in rescuing residents still trapped in Azovstal.

"The lives of those who remain are in jeopardy," he stated.

Russia declared victory in Mariupol on Ukraine's southern Black Sea coast on April 21 after weeks of siege left trapped inhabitants without food, water, or shelter.

Attempts to establish humanitarian corridors to allow civilians to flee have all failed.

On February 24, Moscow invaded Ukraine, claiming it was conducting a "special military operation" to support Russian-backed rebel enclaves in the east. After withdrawing from Kyiv's areas, it is now concentrating its firepower on Ukraine's east.