(NewsNation) — U.N. Secretary-General António Guterres reported progress Thursday after having met with both Ukraine President Volodymyr Zelenskyy and Russian President Vladimir Putin.

There’s an “agreement in principle” to evacuate soldiers and civilians from a besieged steel plant in the Ukrainian port city of Mariupol.

Ukrainian troops defending the steel plant that is the last Ukrainian bulwark in Mariupol say intensive Russian bombing has inflicted more casualties.

The Azov Regiment holed up at the giant Azovstal steel plant posted a video showing people combing through the rubble to remove the dead bodies and help the wounded after a Russian bombing overnight. The video couldn’t be independently verified.

The Azov said the Russians hit an improvised underground hospital and its surgery room, killing an unspecified number of people and wounding others there.

The Russian troops have pummeled the mammoth seaside plant with relentless airstrikes and artillery barrages, trying to uproot its defenders holed up in a 15-mile maze of underground tunnels, passages and bunkers.

Ukrainian officials say up to 1,000 civilians also were sheltering in Azovstal. They are demanding that Russia provides a safe exit for them under the United Nations aegis.

The leaders’ meetings with Guterres come as Russia’s president threatens dire consequences for any country that intervenes on behalf of Ukraine.

Shortly after Zelenskyy and Guterres held a news conference, explosions shook Kyiv, and flames poured out of windows in at least two buildings in the capital city.

Guterres toured areas outside the Ukrainian capital that suffered damage during the Russian advance there.

“What I feel … I imagine my family in one of those houses that is now destroyed and black,” he said.

What Guterres witnessed is allegedly the scene of war crimes — the deliberate targeting of civilians by Russian troops. Bodies were found in the streets of the Kyiv suburb of Bucha earlier this month.

Ukrainian authorities filed criminal charges Thursday against Russian soldiers allegedly involved in mass killings in Bucha.

Guterres urged Russia to cooperate with the International Criminal Court after the bodies of civilians were found in areas once held by Russian forces, some shot with their hands bound.

“The war is an absurdity in the 21st century. The war is evil,” Guterres said. “Civilians always pay the highest price” in any war.

The latest video from the port city of Mariupol shows the war is ongoing with residents clearing debris and taking rescues into their own hands.

As Russian missiles rained down on the Azovstal steel plant where thousands of civilians are taking shelter alongside Ukrainian soldiers, one of those soldiers made an appeal for help.

“Today, it is not 1940,” Ukrainian Army officer Serhiy Volinsky posted. “It is 2022. People here will simply die.”

Zelenskyy hopes evacuations of the steel plant are imminent and called Russian attacks barbaric.

“What we have still is an agreement in principle,” said Farhan Haq. deputy spokesman for the secretary-general. “What we’re trying to do is translate that into an agreement in detail and an agreement on the ground.”

The Associated Press contributed to this report.