Ukraine has claimed that Russia launched a strike on a civilian vessel in the Black Sea right after it left Ukrainian territorial waters.
President Volodymyr Zelensky said there were no casualties, according to preliminary reports.
The vessel carrying Ukrainian grain to Egypt had been hit by a Russian missile.
President Zelensky said Ukraine is one of the key global food security guarantors.
"Domestic stability and normal life in dozens of countries around the world are dependent on the normal and unhindered operation of our food expert corridor," he said.
According to him, Ukraine's food deliveries to African and Middle Eastern countries are critical.
"We will continue to make every effort to safeguard our ports, the Black Sea, and food exports to global markets. This is Ukraine's true priority to protect life and it should be the priority of all countries."
"We are waiting for the world to react. Wheat and food security should never be targets for missiles."
There was no immediate comment from Russia.
