Bucha, a suburb of the Ukrainian capital of Kyiv, has been liberated from Russian forces, its mayor declared.

"March 31 will go down in the history of our settlement and the entire territorial community as a day of liberation from the Russian occupiers by our armed forces,” Mayor Anatolii Fedoruk said in a video posted to Facebook Friday. "Today I state that this day is joyful and it is a great victory of our armed forces in Kyiv region."

Last week, Ukraine's Defense Ministry said Russian forces battling toward Kyiv were able to partially take several northwestern suburbs, including Bucha.

-ABC News' Irene Hanatiyuk

Over 6,200 people were evacuated from regions in southeastern Ukraine Friday by buses and private cars, according to Ukrainian officials.

In the Donetsk region, 3,071 people were evacuated from the besieged port city of Mariupol, officials said.

Earlier Friday, Mariupol officials said an estimated 100,000 civilians remained trapped in the city despite repeated efforts by Ukrainian officials to evacuate them.

Additionally, over 1,700 people were evacuated from the Luhansk region, and over 1,400 from the Zaporizhzhia region, Ukrainian officials said.

-ABC News' Irene Hanatiyuk

Russian and Ukrainian negotiators continued peace talks virtually on Friday, Mykhailo Podolyak, a chief negotiator for the Ukrainians, told ABC News.

"On the table is the key document proposed by the Ukrainian delegation - the Treaty on Security Guarantees," Podolyak said. This proposed agreement provides for the possibility of exit from the war and the prevention of future conflicts.

Ukraine proposed a new system of security guarantees similar to NATO's collective defense clause which would legally require "guarantor countries" to provide arms and impose a "no-fly" zone over Ukraine, in the event of an attack.

Both sides are working on the legal wording of the basic provisions of the contract, Podolyak said.

"The discussion is extremely difficult, since the negotiating positions of the parties are strongly influenced by the daily change in the military situation on all lines of contact," Podolyak said.

-ABC News' Bruno Roeber and James Longman

An International Committee of the Red Cross team that was on its way to Mariupol to facilitate the safe passage of civilians on Friday had to return to Zaporizhzhia. The ICRC said arrangements and conditions made it impossible to proceed.

The ICRC team, which consists of three vehicles and nine personnel, said it will try again on Saturday.

The ICRC said it is critical that parties respect the agreements and provide the necessary conditions and security guarantees, and that it plans to accompany the convoy out of Mariupol to another Ukrainian city.

-ABC News' Cindy Smith

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