The videos show women and children living underground in a dark, damp basement. One mother said they’ve not seen the sun in weeks and will soon run out of food. An old woman, her head bandaged and bloodied, shivers on a cot. A baby wears a plastic bag fastened with duct tape around its small waist — there are no diapers left.

The harrowing footage was posted on YouTube by the Azov regiment, a unit of the Ukrainian armed forces, which said it was filmed in the vast network of tunnels underneath the Azovstal steel plant — Mariupol’s last remaining holdout.

Smoke rises above Azovstal steel plant in Mariupol on April 18. (Alexander Ermochenko/Reuters)

After relentless bombardment by air, sea and sky, Russian troops have taken control of what is left of the rest of the city. Once a thriving port and beloved vacation spot on the Black Sea, much of Mariupol now lies in ruins. The steel plant is the last remaining shelter for hundreds of soldiers and civilians still stuck in the city.

In a clip published last week, a young boy, his cheeks pale, made a heart-wrenching plea for a path out.

I want to get out of here and see the sun. We’ve been here for two months now, and I want to see the sun,” he said. “When they rebuild our houses, we can live in peace. Let Ukraine win this war because Ukraine is our dear home.”

Increasingly, it seems there is little chance of their rescue.

Myhailo Podoliak, adviser to Ukrainian President Volodymyr Zelensky, said on Saturday that Russia was refusing to help save the people of Mariupol and had shown “absolute unwillingness to talk.”

The videos shared by the Azov regiment, which are accompanied by pleas for help, give a sense of the desperate situation unfolding for Mariupol residents left behind. In the absence of journalists on the ground — an Associated Press team, the only Western news media reporting from the city, left in March — and almost no internet or cell service, the clips posted by Azov to social channels are among few windows into the plight of people trapped in the plant.

On Thursday, Ukrainian officials said Russia had carried out airstrikes on a field hospital within the plant. Mariupol’s mayor, Vadym Boichenko, said that more than 600 were injured in the bombing. The attack renewed calls from the United Nations for humanitarian corridors to open up to the city.

UN Secretary-General António Guterres, speaking alongside Zelensky in a press conference in Kyiv, said that the besieged city was a “crisis within a crisis” and that the people stranded there were in desperate need of help. According to Guterres, Russian President Vladimir Putin has agreed in principle for the involvement of the UN and International Committee of the Red Cross in the evacuation of civilians from Azovstal. But so far those corridors have not become a reality. Last week, Putin told his defense minister in Moscow that the plant should bee sealed off but not stormed.

Footage and photos shared by the Azov regiment on Friday shows graphic scenes in what is described as the aftermath of the attack on the makeshift hospital in the plant. CNN could not independently verify the location of the videos.

An Azov commander inside the Azovstal steel complex told CNN on Friday that children from 4-months to 16-years-old were trapped inside — some in cellars and bunkers that are now unreachable because they had been covered by rubble.

We do not know whether the people there are alive or not,” he said.

Some background: The Azov regiment was originally formed in 2014 as the Azov Battalion, to defend Mariupol from attack by Russian-backed separatists. When it was created, it was known for having members with nationalist and neo-Nazi leanings, which Russia has cited to justify its war. But since the regiment was integrated into the Ukrainian military, analysts and Ukrainian officials say it has reformed. The unit has played a major role in defending the city in recent weeks and its soldiers have repeatedly pled for civilians to be evacuated from the plant.