Ukraine's air force said early on Sunday it had destroyed 22 Russian drones in an overnight attack on the southern Odesa region.

Russia "launched several waves of attacks by 'Shahed-136/131' (unmanned aerial vehicles) from the south and southeast", Ukraine's Air Force wrote on Telegram.

A total of 25 Iranian-made Shahed attack drones had been launched and "22 of them were destroyed by… the Air Force in cooperation with the air defense of other components of the Defense Forces of Ukraine", it said.

Following the collapse in July of a United Nations-brokered deal allowing safe shipments from the Black Sea, Russia has ramped up attacks on Ukraine's southern Odesa and Mykolaiv regions, home to ports and infrastructure that are vital for the shipment of grain.

Last month, the first civilian cargo ship sailing through the Black Sea from Ukraine arrived in Istanbul in defiance of the Russian blockade.

Ukrainian President Volodymyr Zelensky said on Saturday that two more vessels had passed through the country's "temporary Black Sea grain corridor".