Russia claimed Wednesday that the United States isn't interested in the rapid progress of negotiations between Russia and Ukraine.

During a speech to students at the Moscow State Institute of International Relations in Russia's capital, Russian Foreign Minister Sergey Lavrov accused Washington of wanting to keep Moscow and Kyiv "in a state of hostilities" for "as long as possible."

"Negotiations are difficult because the Ukrainian side seems to have expressed understanding of the things that should be agreed upon during the negotiations, constantly changing its position, refusing its own proposals," Lavrov said. "It is difficult to get rid of the impression that they are being held by the hand by their American colleagues."

He alleged "it is unprofitable" for the U.S. "that this process be completed quickly."

"They expect to continue pumping weapons to Ukraine. Provocative statements are being made," he added. "Apparently they want to keep us as long as possible in a state of hostilities."

Video has emerged showing the devastation in Ukraine's besieged city of Mariupol.

Drone footage recorded Wednesday and released by a Ukrainian right-wing paramilitary group that has been incorporated into Ukraine's National Guard shows entire neighborhoods destroyed in Mariupol. Mere shells are all that remain of buildings and smoke is still rising from some of the wreckage. The video has been verified by ABC News.

Ukrainian troops are continuing to battle persistent efforts by Russian forces to seize the strategic port city in southeastern Ukraine.

-ABC News' Fergal Gallagher

Belarus announced Wednesday its decision to expel several Ukrainian diplomats and close the Ukrainian Consulate General in Brest.

"The Ukrainian embassy will continue to work in Belarus in a 1+4 format, that is, an ambassador and four staff members," Belarusian Ministry of Foreign Affairs spokesperson Anatoly Glaz said in a statement, according to the state-run news agency BelTA.

Fierce fighting between Russian and Ukrainian forces continued in Mariupol on Wednesday morning, with the Ukrainian government warning that as many as 100,000 civilians -- or 22% of the besieged port city's original population -- remain trapped there.

One Mariupol resident, Natalia, who managed to escape with her elderly parents and four cats, told ABC News her home had no electricity or heat and that she would have to scavenge for food and other supplies under Russian bombardment. She recalled seeing bodies strewn in the streets because residents had no choice but to leave them there.

"We understood anytime we might be killed by the next bomb," Natalia said during an interview Tuesday.

Pro-Russia separatist forces from the self-declared Donetsk People's Republic in Ukraine's disputed Donbas region said Wednesday that 562 civilians, including 110 children, were evacuated from encircled Mariupol to the occupied town of Bezymenne in the past 24 hours. A total of 4,621 civilians were evacuated from Mariupol between March 5 and March 23, according to the separatist forces.

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