Russian troops fired gas into a crowd of peaceful protesters in the southern Ukrainian city of Kherson on Tuesday.

Video from the scene, taken by journalists, shows projectiles landing in a square in central Kherson where residents had gathered to protest Russia's occupation of the city. Loud bangs can be heard and the crowd suddenly disperses as people attempt to flee the smoke and gas emitting from the canisters around them. People are seen coughing and covering their faces as they run away.

-ABC News' Julia Drozd and Fergal Gallagher

ABC News' team in Kyiv reported hearing several loud explosions just before 1 p.m. local time.

The Ukrainian capital was reported to be relatively quiet earlier Tuesday, which marks the first full day of a 35-hour curfew, set to expire Wednesday morning.

The Ukrainian Ministry of Defense said Tuesday that Ukrainian troops expelled Russian forces from Makariv, a suburb of Kyiv, after a fierce battle. However, Russian forces pushing toward Kyiv were able to take partial control of other northwestern suburbs, Bucha, Hostomel and Irpin, according to the defense ministry.

Ukrainian President Volodymyr Zelenskyy said he received a telephone call from Pope Francis on Tuesday.

Zelenskyy made the comment at the start of his 11-minute impassioned speech to Italy's parliament via video link, after which he received a standing ovation.

Ukraine's ambassador to the Holy See, Andryi Yurash, later took to Twitter to confirm the call, saying Zelenskyy had a "very promising" conversation with the pontiff and invited him to visit Ukraine.

The Vatican confirmed to ABC News that the call took place but did not offer further details.

-ABC News' Phoebe Natanson

Several fires have erupted within the area around Ukraine's Chernobyl nuclear power plant, according to a press release from the Ukrainian parliament, which cited satellite images from the European Space Agency.

The Ukrainian parliament said the fires in the Chernobyl Exclusion Zone, a 1,000-square-mile restricted area of deserted land surrounding the shuttered plant, were likely caused by "shelling or arson" at the hands of Russian forces, which seized the site last month.

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