KYIV, July 31 - A Ukrainian grain mogul and his wife were killed after the southern city of Mykolaiv came under intense shelling on Sunday, a week after Russia has agreed to unblock grain exports from Ukraine.

Grain tycoon Oleksiy and his wife, Raisa, died in the attack, according to a statement from President Volodymyr Zelensky, CNN reported. Ukrainian media reported that both were killed when a Russian missile had hit the bedroom of their house in the middle of the night.

Vadaturskyy was the founder of Mykolaiv-based Nibulon, one of Ukraine's largest grain producing and export companies.

"This is a great loss for Mykolaiv region 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.

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.

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." (cnn/ez)