CNN  — 

A Ukrainian grain mogul and his wife were killed after the southern city of Mykolaiv came under intense shelling on Sunday, according to Ukrainian officials, as Russian President Vladimir Putin used his nation’s Navy Day to issue more militaristic threats to anyone undermining Russia’s “sovereignty and freedom.”

Grain tycoon Oleksiy Vadaturskyy and his wife, Raisa, died in the attack, according to a statement from Ukrainian President Volodymyr Zelensky. Vadaturskyy was the founder of Mykolaiv-based Nibulon, one of Ukraine’s largest grain producing and export companies.

The businessman’s death was a “great loss for Mykolaiv … and all of Ukraine,” Zelensky said. “For more than 50 years of his career, Oleksiy Vadaturskyy made an invaluable contribution to the development of the region and the development of the agricultural and shipbuilding industries of our country.”

Mykolaiv Mayor Oleksandr Senkevych said cluster munitions blew out windows and destroyed balconies. “Mykolaiv was under mass shelling today. Probably the strongest one of all time,” he said in a statement.

A CNN team on the ground heard the explosions caused by the strikes and saw fires that broke out in the shelling. Residents interviewed by CNN also said it was the heaviest shelling in the city since the start of the war.

In a speech commemorating Russia’s Navy Day in Saint Petersburg, Putin did not make any mention of Russia’s war in Ukraine, but said his country’s “current situation is demanding very decisive actions.”

“We will provide protection firmly and by all means. The key here is the capabilities of the Navy, which is able to respond with lightning speed to anyone who decides to encroach on our sovereignty and freedom,” Putin said.

Putin said delivery of the country’s Zircon hypersonic cruise missile systems would begin in the coming months. Russia said in May that it successfully tested the Zircon missile over a distance of 1,000 kilometers (621 miles).

Russian President Vladimir Putin delivers a speech marking Navy Day, in St. Petersburg on July 31, 2022.

‘True hero’

Vadaturskyy and his wife were sheltering in the basement at home when they were killed in a direct hit that reduced parts of their mansion to debris. It remains unclear whether he was intentionally targeted by the Russians.

A statement from Vadaturskyy’s company, Nibulon, said he was a “true hero and patriot” who had stayed in Mykolaiv to help the strategically important port throughout Russia’s invasion.

“He always believed in Ukraine and directed his efforts to its development and prosperity,” the statement said.

Neighbors expressed their shock and anger at the attack.

“We don’t know what to do. We hate Russia,” said Maxim, who has lived in the area for almost 20 years. “It’s unbelievable that in one moment it can destroy everything.”

Grain mogul Oleksiy Vadaturskyy and his wife, Raisa, died in a Russian attack on the city of Mykolaiv on Sunday.

Accusations of war crimes

Separately, at least three people were killed and eight injured in fighting in eastern Ukraine, according to the Donetsk military-civilian administration, which said villages in the region were targeted by artillery, Russian Grad missiles and Uragan rockets.

“11 private residential buildings and a high-rise building, a police station, a market, a canteen were damaged, and three fields were burned,” the administration said.

The Ukraine General Staff said Russian forces were attacking the front lines in the Donetsk and Luhansk regions.

A firefighter responds to shelling in Mykolaiv, Ukraine, on Sunday, July 31.

Zelensky on Saturday called on the remaining residents of the Donetsk region to urgently evacuate in what he called a “government decision.”

“Everything is being organized. Full support, full assistance – both logistical and payments,” he said in his nightly address. “We only need a decision from the people themselves, who have not yet made it for themselves.”

A strike on a prison in separatist-held eastern Ukraine on Friday resulted in the deaths of at least 40 prisoners. The Olenivka prison near Donetsk has been used to house many of the Ukrainian soldiers who surrendered at the Azovstal plant in Mariupol several months ago.

UK Ambassador to Ukraine Melinda Simmons said the strike was part of a pattern “the worst kind of human rights abuses” in her twitter on Saturday. “Olenivka needs investigating. It looks like part of an increasingly worrying pattern of the worst kind of human rights abuses, and possible war crimes, being committed in the occupied East of Ukraine with impunity,” the ambassador tweeted.

Zelensky said the attack was “a deliberate war crime by the Russians.”

Ukrainian intelligence said the strikes were carried out by the Russia mercenary group Wagner and were not coordinated with the Russian Ministry of Defense. CNN cannot independently verify the accusations made by Ukrainian military intelligence.

Russia has blamed Ukraine for the attack.