The ship Brave Commander has left the Ukrainian port of Pivdennyi, carrying the first cargo of humanitarian food aid bound for Africa from Ukraine since Russia's invasion, Refinitiv Eikon data showed on Tuesday.

Ukraine's grain exports have slumped since the start of the war because of the closure of its Black Sea ports, driving up global food prices and sparking fears of shortages in Africa and the Middle East.

Moscow calls its action in Ukraine a "special military operation".

Three Black Sea ports were unblocked last month under a deal between Moscow and Kyiv, brokered by the United Nations and Turkey, making it possible to send hundreds of thousands of tonnes of Ukrainian grain to buyers.

The Brave Commander, with 23,000 tonnes of wheat aboard, left for Djibouti with supplies destined for consumers in Ethiopia, Ukraine's infrastructure ministry said.

"The ministry and the United Nations are working on ways to increase food supplies for the socially vulnerable sections of the African population," it said in a statement.

Ukraine can export 3 million tonnes of grain from its ports in September and may in the future be able to export 4 million tonnes monthly, Deputy Infrastructure Minister Yuriy Vaskov said.

He said Ukraine had received applications for 30 ships to come to Ukraine in the next two weeks to export grain, while the total export volume so far was about 600,000 tonnes.

Turkey's defence ministry said that five ships left Ukrainian ports on Tuesday carrying corn and wheat, three from Chornomorsk and two from Pivdennyi, bringing the total of ships to leave under the deal to 21.

Four more ships, bound for Ukraine, were to be inspected on Tuesday by the joint co-ordination centre, set up by Russia, Turkey, Ukraine and the United Nations in Istanbul.

Despite unblocked ports, Ukraine's grain exports are down 46% year on year at 2.65 million tonnes so far in the 2022/23 season, the agriculture ministry said this week.

Ukraine exported 948,000 tonnes of grain in the first half of August, down from 1.88 million tonnes in the same period a year earlier.