The owner of one of Ukraine's largest grain producing and exporting companies and his wife were killed in a Russian strike in the southern Ukrainian port city of Mykolaiv, the local governor said Sunday.

Oleksiy Vadatursky, founder and owner of agriculture company Nibulon, and his wife were killed in their home, Mykolaiv Governor Vitaliy Kim said on Telegram. Vadatursky was one of Ukraine’s richest men and was said to be worth more than 400 million euros ($408 million).

Mykolaiv was hit by heavy Russian strikes overnight and on Sunday morning that officials described as "probably the most powerful" on the city of Russia's entire five-month-old invasion of Ukraine.

Headquartered in Mykolaiv, a strategically important city that borders the Russia-occupied Kherson region, Nibulon specializes in the production and export of wheat, barley and corn, and it has its own fleet and shipyard.

President Volodymyr Zelenskyy described Vadatursky’s death as "a great loss for all of Ukraine,” saying in a statement the businessperson had been in the process of building a modern grain market involving a network of transshipment terminals and elevators.

Russia’s invasion of Ukraine, the biggest conflict in Europe since World War II, has stoked an energy and food crisis that is shaking the global economy. Both Ukraine and Russia are leading suppliers of grain.

Zelenskyy said on Sunday the country may harvest only half its usual amount this year due to the invasion.

"Ukrainian harvest this year is under the threat to be twice less,” suggesting half as much as usual, Zelenskyy wrote in English on Twitter. "Our main goal – to prevent global food crisis caused by Russian invasion. Still grains find a way to be delivered alternatively,” he added.

Ukraine has struggled to get its product to buyers via its Black Sea ports because of the war.

But an agreement signed under the stewardship of the United Nations and Turkey on July 22 provides for safe passage for ships carrying grain out of three southern Ukrainian ports.

There is a high possibility that the first grain-exporting ship will leave Ukraine’s ports on Monday, Turkish Presidential Spokesperson Ibrahim Kalın said on Sunday.