Turkish President Recep Tayyip Erdogan is expected to call on his Russian counterpart Vladimir Putin to return to an agreement that allows Ukraine to ship its grain through the Black Sea.

The leaders are scheduled to meet in the southern Russian city of Sochi on Monday.

In July, Russia quit the deal mediated by Turkey and the United Nations, fanning fears of a global food crisis.

However, it remains unclear whether the meeting will pave the way for resumption of the accord as Russian forces attacked a port in southern Ukraine where grain shipping infrastructure is located.

The Russian defense ministry said on Sunday that its drone strikes had targeted fuel storage facilities at the port in the region of Odesa.

The Ukrainian military said its troops had shot down 22 of the 25 Iranian-made drones deployed in the Russian attacks. But it said port infrastructure on the Danube River was hit, causing a fire and injuring two people.

The Danube has served as a main alternative route for Ukraine to export its agricultural products because Russia's withdrawal from the grain deal means its forces could attack ships passing through the Black Sea.

Meanwhile, the Sunday edition of a UK newspaper, The Observer, carried its exclusive interview with a Ukrainian general leading a counteroffensive in the southern region of Zaporizhzhia.

The general said his forces have breached Russia's first defensive line and are now consolidating their hold on territory seized in recent fighting.

He said Moscow "is pulling up reserves, not only from Ukraine but also from Russia." But he added that sooner or later Russia "will run out of all the best soldiers," giving Ukrainian troops "an impetus to attack more and faster."