The International Atomic Energy Agency, the United Nations' nuclear watchdog, said on Friday that radiation around the Chernobyl nuclear power plant is normal.

"General radiation around the plant is quite normal," IAEA Director General Rafael Mariano Grossi said at a press conference.

There have been instances of relatively higher levels of localized radiation, which may have been caused by heavy vehicles moving in the area, the IAEA said.

The IAEA said it does not have any evidence that people were possibly contaminated.

Russia has not discussed its withdrawal from Chernobyl with the IAEA, the organization said.

"On the issue of radiation we are in consultation with the Ukrainian side," Grossi said.

Grossi repeatedly stressed the unpredictability of working in a war zone, saying things may not have gone strictly according to plan.

"In case there was an emergency taking place, we are setting up a mechanism whereby we can send a team to assist almost immediately," Grossi said.

-ABC News' Guy Davies

The International Committee of the Red Cross is leading a large convoy on Friday to help civilians escape the hellscape that has become of Ukraine's besieged port city of Mariupol, according to Crystal Wells, a spokesperson for the Geneva-based humanitarian organization.

"This effort has been and remains extremely complex," Wells told ABC News in a statement. "There are a lot of moving parts and not all the details are yet in place to ensure that this happens in a safe manner today. We remain hopeful, we are in action moving toward Mariupol, but it’s not yet clear that this will happen today."

According to Wells, the three ICRC vehicles, carrying nine ICRC staff, are leading vehicles from other organizations -- "potentially 54 buses." Images circulating on social media show other civilian vehicles joining the convoy.

"Our presence puts a humanitarian marker on this movement of people, giving the convoy additional protection and reminding all sides of the civilian, non-military, humanitarian nature of the operation," Wells said. "If and when it does happen, the ICRC's role as a neutral intermediary will be to lead the convoy out from Mariupol to another city in Ukraine. We’re unable to confirm which city at the moment as this is something the parties must agree to."

The situation in Mariupol "is horrendous and deteriorating, and it’s now a humanitarian imperative that people be allowed to leave, and aid supplies be allowed in," according to Wells.

"We're running out of adjectives to describe the horrors that residents in Mariupol have suffered," she added. "The people of Mariupol have suffered weeks of heavy fighting, with dwindling water, food and medical supplies."

The ICRC has had "open communication channels" with both Ukraine and Russia, Wells said, "but ensuring that all the details are agreed upon and well understood by all sides, and then communicated down the chain of command, and to the residents of Mariupol, is a challenge, and one that continues to take time to sort out."

"The details that we insist are cemented in place include the exact safe passage route, its exact start time, and its duration," she noted. "We have to be certain that a cease-fire holds. We have to be certain that this humanitarian convoy can safely move through military checkpoints."

-ABC News' Brian Hartman

Ukrainian forces have retaken the villages of Sloboda and Lukashivka to the south of Chernihiv, located along one of the main supply routes between the northern city and Ukraine's capital, Kyiv, the U.K. Ministry of Defense said Friday in an intelligence update.

"Ukraine has also continued to make successful but limited counter attack to the east and north east of Kyiv," the ministry added. "Both Chernihiv and Kyiv have been subjected to continued air and missile strikes despite Russian claims of reducing activity in these areas."

Ukraine has declined to comment on Russia's accusation that it carried out airstrikes on an oil depot in the Russian city of Belgorod early Friday.

"We do not comment on Russian fakes," Volodymy Fityo, spokesperson for the Ukrainian Ground Forces, told ABC News. "And we do not comment on the words of Russian officials who speak under the influence of substances."

Earlier Friday, Belgorod Oblast Gov. Vyacheslav Gladkov said in a statement via Telegram that two low-flying Ukrainian helicopters had entered Russian airspace and fired on an oil depot in Belgorod city, setting the building ablaze.

The depot run by Russian energy giant Roseneft is located about 21 miles north of the border with Ukraine. Two employees were injured but are expected to survive, while all other staff have been safely evacuated from the building, according to Gladkov.

Verified videos circulating online show an attack on an oil depot in Belgorod and the aftermath.

-ABC News' James Longman

All Russian troops have left the Ukrainian cities of Kyiv and Chernihiv, withdrawing north toward the borders of Belarus and Russia to consolidate before likely redeploying to the Donbas region in eastern Ukraine, a senior U.S. defense official told reporters Wednesday.

But even with the Russians gone, the territory remains treacherous.

"There are some indications that they left behind mines and things like that, so the Ukrainians are being somewhat careful in some areas north of Kyiv as they begin to clear the ground and clear the territory and re-occupy it," the official said.

While the U.S. hasn't yet seen these troops redeploy elsewhere in Ukraine, it'll likely happen soon, according to the official. Ukrainian forces are preparing for a major fight in Donbas, the official said.

The official also said the Pentagon is "monitoring" an apparent nitric acid explosion in Ukraine's Luhansk region, which Russia blamed on Ukraine.

"We've seen the Russians claim that this was a Ukrainian attack on this. We do not believe that is true," the official said. "We do believe that the Russians are responsible, but exactly what they used when they did it, why they did it, what the damage is, we just don't have that level of detail," the official said.

The official also noted that a small number of Ukrainians currently in the U.S. for "professional military education" were pulled aside for a couple days of training on Switchblade drones, which the U.S. is sending overseas as part of its military aid, according to the official.

"Although it's not a very difficult system to operate, we took advantage of having them in the country to give them some rudimentary training on that," the official said.

-ABC News' Matt Seyler