Ukrainian President Volodymyr Zelenskyy issued a new address Saturday updating the progress of the country's defense against Russian forces.

Ukrainian forces are regaining control of the Kyiv and Chernihiv regions, according to the president.

"There are more and more Ukrainian national flags in the areas that have been temporarily occupied," Zelenskyy said.

Zelenskyy, however, said his country hasn't received any new weapon systems from the West and chastised Western allies.

"Every Russian missile that hit our cities and every bomb dropped on our people, on our children, only adds black paint to the history that will describe everyone on whom the decision depended; [the] decision whether to help Ukraine with modern weapons," he said.

-ABC News' Jason Volack

Acclaimed Ukrainian photographer Maksim Levin was found dead by police in the Kyiv region, a Ukrainian online publication confirmed.

Levin went missing on March 13 while covering fighting in the village of Moshchun, Ukraine, with Oleksiy Chernyshov, who has not yet been found. Intense fighting broke out in the area where they were.

Levin worked as a photojournalist, documentary photographer and cameraman for many Ukrainian and international publications, according to .

He worked in the editorial office of for more than 10 years, and has also worked with Reuters, BBC, TRT World, Associated Press and Hromadske.

-ABC News' Yulia Drozd

The Ukrainian national flag was raised above the Chernobyl nuclear power plant Saturday at 11:00 a.m. local time, as workers sung the national anthem and celebrated the departure of Russian troops who had occupied the site for weeks.

"The flag-raising ceremony was attended by the station's operational personnel, who have been ensuring and continue to ensure the nuclear and radiation safety of the facilities during the difficult conditions of the occupation," Energoatom, Ukraine's state enterprise which operates its nuclear power stations, posted on its Telegram channel.

Roscosmos, the Russian state space corporation, said it will present the Russian government with proposals for discontinuing international cooperation on the International Space Station.

"Specific proposals from Roscosmos on the timeframe for ending cooperation on the ISS with the space agencies of the United States, Canada, the European Union and Japan will be submitted to our country's administration in the near future," Roscosmos CEO Dmitry Rogozin said on his Telegram channel.

Resumption of normal cooperation with ISS partners is only possible if the sanctions are fully lifted, Rogozin said.

"I believe that restoration of normal relations between the partners on the International Space Station and other joint projects is possible only if the illegal sanctions are lifted fully and unconditionally," he wrote.

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