Russia-Ukraine updates: Russian missiles hit close to nuclear reactors: IAEA director

At least 15 people were killed and two dozen more are feared trapped in rubble after Russian Uragan rockets slammed into a five-story apartment building in eastern Ukraine's Donetsk region, local officials said on Sunday.

Search-and-rescue workers were combing through the rubble for survivors on Sunday.

The missile strike came as Ukrainian officials reported clashes with Russian troops on the frontline in the eastern and southern Ukraine.

Donetsk Governor Pavlo Kyrylenko said the strike on the apartment building occurred Saturday evening in the town of Chasiv Yar. The regional emergency service said Sunday that the death toll had climbed to 15 and that 24 more people could still be buried under the rubble.

"We ran to the basement, there were three hits, the first somewhere in the kitchen," a local resident, who gave her name as Ludmila, told rescuers as they removed a body wrapped in a white sheet and cleared rubble using a crane as well as their hands. "The second (strike), I do not even remember, there was lightning, we ran towards the second entrance and then straight into the basement. We sat there all night until this morning."

Andriy Yermak, chief of staff to Ukrainian President Volodymyr Zelenskyy, said in a Telegram post that the strike was "another terrorist attack" and that Russia should be designated as a state sponsor of terrorism as a result.

Russian officials claimed its forces struck Ukrainian army hangars storing U.S.-produced M777 howitzers, a type of artillery, near Kostyantynivka in Donetsk region, but, so far, has not claimed responsibility for the missile strike on the residential building in Chasiv Yar.

-ABC News' Christine Theodorou

U.S. Secretary of State Antony Blinken said Sunday that the Russian invasion of Ukraine has "significantly exacerbated" a global food insecurity crisis and may have contributed to the economic collapse of Sri Lanka.

“What we are seeing around the world is growing food insecurity that has been significantly exacerbated by the Russian aggression against Ukraine and as we've had opportunity to discuss in recent days, there are more than 20 million tons of grain that are sitting in silos in Ukraine that can't get out can't get out to feed people around the world," Blinken told reporters during his first official visit to Thailand.

He noted that he discussed the global food insecurity crisis during meetings with Thai Deputy Prime Minister and Foreign Minister Don Pramudwinai and said a memorandum of understanding the two leaders signed commemorating a new collaboration will "make it easier for Thailand and the United States to quickly share information and consult on possible supply chain disruptions so that we can actually take early action to mitigate problems."

Blinken added that the impact of this Russian invasion of Ukraine is being felt around the world, particularly in Sri Lanka, where the prime minister said late last month that the island nation’s debt-laden economy had “collapsed” and run out of money to pay for food and fuel. The economic turmoil has prompted massive protests in Sri Lanka and over the weekend demonstrators stormed the president's residence in the capital of Colombo.

"So we're seeing the impact of this Russian aggression to play out everywhere," Blinken said. "Again, it may have contributed to the situation in Sri Lanka. We’re concerned about the implications that it has around the world."

-ABC News' Lauren Minore

The Biden administration announced a new $400 million military aid package for Ukraine on Friday that includes four more High Mobility Artillery Rocket Systems, or HIMARS.

Ukraine will now have a total of 12 of these precision rocket launcher systems, which have been "especially important and effective in assisting Ukraine in coping with the Russian artillery battle in the Donbas," a senior defense official told reporters Friday.

The rockets have a range of 43 miles. The official said that Ukraine has been striking at Russian targets deep behind enemy lines but has not used them to strike inside Russia.

The new aid package also includes 1,000 new "greater precision" artillery. The name of the system was not shared for security purposes, the official said.

The new aid package is the 15th use of the presidential drawdown authority to give existing U.S. military stocks to Ukraine.

-ABC News' Luis Martinez

Russia considers nuclear weapons only as a deterrent, according to Valentina Matviyenko, Chairman of the Russian Federation Council.

"Russia views nuclear weapons only as a deterrent," Matviyenko said Thursday at a press conference.

The official noted that Russia has “clearly and strictly prescribed those exceptional cases when [nuclear weapons] can only be used in response to -- God forbid that this never happens -- a nuclear attack."

“We behave like a civilized country, and we do it openly,” Matviyenko added.

-ABC News' Edward Szekeres, Yulia Drozd, Max Uzol, and Fidel Pavlenko