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Video circulating online shows explosions and smoke coming from the Azovstal Iron and Steel Works plant in Mariupol.

The footage was released Thursday by the Azov Regiment, a far-right group now part of the Ukrainian military that was among the units defending Mariupol and is holed up inside the Azovstal plant with others. In a statement alongside the video posted on Telegram, the group said that Russian forces were keeping the plant "under heavy fire," using "aircraft, artillery and infantry."

ABC News was unable to verify the date that the video was taken.

In recent days, Ukraine and Russia have offered conflicting accounts of what's taking place at the Azovstal plant. Ukrainian fighters claimed that Russian forces started storming the plant this week, which Russia has denied and instead claimed that its troops have "securely blocked" the sprawling industrial site.

Hundreds of Ukrainian fighters and civilians are said to be trapped inside the Azovstal plant, the last pocket of resistance in Mariupol as Russian forces declare full control over the strategic Ukrainian port city.

Russia's so-called special military operation in neighboring Ukraine is going according to plan, according to Kremlin spokesman Dmitry Peskov.

"The operation has been going to plan," Peskov said during a press briefing in Moscow on Friday.

When asked about reports that Putin's inner circle was not informed about the start of the operation, Peskov told reporters: "As you understand, naturally, information about the special military operation cannot be shared widely the day before it begins."

"That is because, clearly, such classified information is always shared with a rather limited circle of persons. This is an absolutely normal practice," he added. "The very essence of this operation does not imply that information about it will be shared widely."

Presiding over her first open meeting of the United Nations Security Council since the Russian invasion of Ukraine began, U.S. Ambassador to the U.N. Linda Thomas-Greenfield implored representatives still clinging to neutrality to speak out against Russian aggression.

"The truth is well known. Russia is the only perpetrator of this war. So it's hard to understand why some council members continue to call on all parties to desist," Thomas-Greenfield said, calling out countries like Brazil, India, and to some extent—China.

"Let's call a spade a spade. Members should call on Russia explicitly to stop its aggression against Ukraine," she said.

Speaking in her capacity as the United States’ permanent representative and not as the temporary president of the council, Thomas-Greenfield lamented that Russian envoys had repeatedly used the body to spread disinformation.

"Three months ago, Russian representatives told this council they had no intention to invade Ukraine. Now, Russia claims the attacks aren’t real or never happened," she said. "Russia even claims that Ukraine is attacking itself, that they bombed their own buildings, attacked their own people and assaulted their own democracy. These lies defy all logic, all evidence and common sense."

-ABC News' Shannon Crawford

Martin Griffiths, the United Nations under-secretary-general for humanitarian affairs and emergency relief coordinator, confirmed another convoy is heading to the Azovstal Iron and Steel Works plant in Mariupol and is expected to arrive on Friday to evacuate more trapped civilians.

"As we speak, a convoy is proceeding to get to Azovstal by tomorrow morning, hopefully, to receive those civilians remaining in that bleak hell that they have inhabited for so many weeks and months and take them back to safety," Griffiths said Thursday at the International Donor's Conference in Warsaw, Poland.

"This elaborate and dangerous operation has taken days and a herculean effort in coordination, advocacy agreements, deployment partnership to achieve," Griffiths said. "It would have been worth it to save one person. And we're now trying to do it for more, but it's a sobering reminder of the difficulties of operation for the safety and protection of the civilians of Ukraine."

Though many people have been evacuated this week, hundreds of Ukrainian fighters and civilians are said to still be trapped inside the plant. The sprawling industrial site is the last pocket of resistance in Mariupol as Russian forces claim to have taken full control of the strategic Ukrainian port city.