Nova Kakhovka, a city in southern Ukraine home to a strategic hydroelectric power plant, is in the hands of Russian forces, Mayor Volodymyr Kovalenko said Sunday.

"Nova Kakhovka in the Kherson Oblast is completely under the control of Russian troops, they seized the city executive committee, removed all Ukrainian flags from buildings," Kovalenko said in a statement on Telegram, according to an NBC News translation. 

It was unclear if Russian forces had taken control of the power plant. 

The Kherson region, which borders Crimea, was once served by a canal that brought water from the Dnieper River, which also churns electricity at the Kakhovka Hydroelectric Station. In 2017, Ukraine built a dam that blocked the canal's supply of water from the river to Crimea. 

Invading Russian troops have already destroyed the dam in the Kherson region, Reuters reported, allowing for the water to flow freely to the occupied peninsula. 

As Ukraine starts its fourth day fending off Russian troops and munitions, a Kyiv official declared Sunday that the capital city was still in the hands of Ukrainians.

"The situation in Kyiv is calm, the capital is completely controlled by the Ukrainian army and defense," Mykola Povoroznyk, first deputy head of the Kyiv City State Administration, said on messaging service Telegram.

He warned that it was not news to savor; the city was under attack by Russian forces. "There were several clashes with sabotage groups at night," Povoroznyk said.

Ukraine's minister of defense, Oleksiy Reznikov, said early Sunday that forces fending off the Russian offensive in Kyiv have made history. "Three days changed our country and the world forever," he said on Facebook.

"I see a heroic army, a civil guard, fearless border guards, selfless rescuers, reliable police officers, tireless medical angels," Reznikov said on Facebook. 

He also praised thousands of Ukrainians who took up arms in defense of Kyiv and their country. "You are seen by all, the whole world!" he wrote.

"Saturday Night Live" opened its first show since the Beijing Winter Olympics with a stunning and solemn performance by the Ukrainian Chorus Dumka of New York.

Singing "Prayer for Ukraine," the approximately 30-member group appeared in traditional white vyshyvanka. Ukraine's national flower, sunflowers, adorned the stage around a table with candles that spelled out "Kyiv." 

It was "SNL's" way of urging peace as Russia invaded Ukraine following its initial offensive Thursday morning.

A U.N. office estimated there have been at least 240 confirmed civilian casualties in Ukraine since Russia attacked, with at least 64 deaths. 

The chorus was founded after World War II by Ukrainian immigrants who wanted to preserve their cultural heritage in a new homeland, according to Ukrainian Weekly. It is now 72 years old and is composed strictly of nonprofessional performers.

Its Facebook page says the group performs work by Ukrainian composers but that its genres can include classical, sacred and folk choral.

Social media reaction to the chorus, introduced by Kate McKinnon and Cecily Strong, was heavily favorable, with some calling it powerful, beautiful and just right. The Christian hip-hop artist Tedashii tweeted that the performance honored "those fighting for their life in Kiev."

Alphabet Inc's Google on Saturday barred Russia's state-owned media outlet RT and other channels from receiving money for ads on their websites, apps and YouTube videos, similar to a move by Facebook after the invasion of Ukraine.

Citing "extraordinary circumstances," Google's YouTube unit said it was "pausing a number of channels’ ability to monetize on YouTube." These included several Russian channels affiliated with recent sanctions, such as those by the European Union.

Google is also barring Russian state-funded media outlets from using its ad technology to generate revenue on their own websites and apps.

In addition, the Russian media will not be able to buy ads through Google Tools or place ads on Google services such as search and Gmail, spokesman Michael Aciman said.

"We’re actively monitoring new developments and will take further steps if necessary," Aciman said.

Videos from affected media will also come up less often in recommendations, YouTube spokesperson Farshad Shadloo said. He added that RT and several other channels would no longer be accessible in Ukraine after a Ukrainian government request.

Russia received an estimated $7 million to $32 million over the two years to December 2018 from ads across 26 YouTube channels it backed, digital researcher Omelas told Reuters at the time.

YouTube has previously said it did not treat state-funded media channels that comply with its rules differently from others when it comes to sharing ad revenue.

Ukrainian former tennis player Sergiy Stakhovsky enlisted in his country's reserve army last week prior to Russia's invasion, he said, despite a lack of military experience, although he can handle a gun.

The 36-year-old Stakhovsky, who won four ATP titles and had a shock win over Roger Federer in the second round of Wimbledon in 2013, said on Saturday he was willing to take up arms in Ukraine's defense.

"Of course, I would fight, it's the only reason I'm trying to get back," Stakhovsky told Sky News.

"I signed up for the reserves last week. I don't have military experience, but I do have experience with a gun privately.

"My dad and brother are surgeons, they are stressed out, but I speak to them frequently — they sleep in the basement.

"None of us believed that this could happen, and yet it happened."

Former heavyweight boxing champion Wladimir Klitschko also enlisted in Ukraine's reserve army this month, saying that love for his country compelled him to defend it.

Russian munitions struck a radioactive waste site in Kyiv, prompting some concern that the effects won't be known until the shelling and missile fire stops, government officials in Ukraine said Sunday. 

The State Inspectorate for Nuclear Regulation of Ukraine said in a statement that the capital branch of the government Radon Association reported seeing falling missiles on security cameras. 

"It is currently not possible to assess the extent of the destruction," the state office said, according to a translation of its statement. 

Experts from the Ukrainian State Association Radon, or Radon Association, reported the attack by phone after seeing it via security video, the inspectorate said. They had taken shelter and viewed the offensive via a remote video system intended for security, it said. The site's automated reporting system had failed.

Now those personnel are pinned down until the offensive at their location ends, the inspectorate said.

Assessment will happen in the wake of Russia's mission, it said. At the same time, the inspectorate believes there is no radioactive threat to people outside of a buffer zone intended to protect communities from radioactive waste sites.

Ukraine has more than a half dozen of these regional sites, including the Kyiv SISP, for State Interregional Specialized Plants for Radioactive Waste Management. They were built to accept waste from the use of radiation in medicine, science and "different industries," according to the government.

Russian forces blew up a gas pipeline in the northeastern Ukrainian city of Kharkiv, Ukrainian officials said Sunday.

Video shared by State Special Communications' Telegram channel showed a rising fireball similar to a mushroom cloud. Officials reassured in the post that was not a nuclear strike.

"In Kharkiv, the occupiers blew up a gas pipeline," the communications office said.

More than 200 miles to the west near Vasylkiv, south of the capital of Kyiv, a Russian ballistic missile attack set an oil depot on fire, officials said. The flames could reportedly be seen from Kyiv, and fighting was reported to be preventing emergency services from working to extinguish the blaze.

Ballistic missiles struck the city of Vasylkiv, south of Kyiv, and an oil plant was on fire, the mayor said as a Russian attack in the country continued for a fourth day.

"You all can see what is happening right now, you see the fire," Vasylkiv Mayor Natalia Balasinovich said in a video message.

Alexey Kuleba, head of the administration in Kyiv Oblast, said on Facebook that the missile strike caused a fire at the oil depot in the village of Kryachky, just outside of Vasylkiv.

Fighting was ongoing and prevented emergency services from extinguishing the fire, according to Kuleba. "We are in danger of an ecological catastrophe. We do everything possible to prevent this!" he said in the statement.

Ballistic missiles also struck an airfield, the mayor said. Vasylkiv is around 20 miles south of the capital of Kyiv. The fire could reportedly be seen from there.

Premise, a San Francisco-based tech company that pays users around the world to share market research and intelligence information with companies and governments, said it suspended its activities in Ukraine on Friday “out of an abundance of caution” after Ukrainian officials accused it of assisting Russia.

The General Staff of the Armed Forces of Ukraine alleged in a Facebook post that enemies were using Premise’s smartphone app to collect data in the western city of Stryi and other parts of the country for the Kremlin.

Premise CEO Maury Blackman said in a statement on Friday that the accusations were “unequivocally false” and that the company does not work for the Russian military or government. “Our company and our team worldwide strongly support Ukraine and the Ukrainian people defending themselves against this illegal act of aggression by Russia,” he said.

Premise did not immediately respond to a request for comment.

In a separate news release also published on Friday, Blackman said that “the public statement of the Ukraine Defense Ministry that has gotten circulation is incorrect.”

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