Ukraine said Wednesday that Russian strikes on its sea and river ports had destroyed 270,000 tonnes of grain in the space of a month, as Moscow pounds its export infrastructure.

Since July's collapse of the UN-brokered Black Sea grain deal, which aimed to ensure safe grain shipments from Ukraine, Moscow has bombarded Ukrainian ports on the sea and Danube river.

"Russia is systematically hitting grain tanks and warehouses to stop agricultural exports," Infrastructure Minister Oleksandr Kubrakov said in a post on social media.

"In total, 270,000 tonnes of grain have been destroyed in a month of attacks on ports," he added.

Last night alone, an attack had reduced the port of Izmail's export capacity by 15 percent and that the port of Reni lost 35,000 tonnes of grain, he said.

"This is the eighth attack on port infrastructure since Russia withdrew from the (grain deal)," Kubrakov added.

Russia's withdrawal from the deal last month prompted both sides to warn ships approaching ports could be considered military targets, effectively revoking safe navigation in the area.

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