KYIV (Reuters) -Russia destroyed Ukrainian grain warehouses on the Danube River and wounded six people in a drone attack on Monday, expanding the target area of an air campaign that it launched last week after pulling out of the Black Sea grain deal, Ukraine said.

Russia has pounded food export facilities in Ukraine's Odesa region in almost nightly attacks since it withdrew from a UN-brokered wartime agreement that allowed global grain producer Ukraine to export food via the Black Sea.

The attacks have mostly targeted facilities in the major sea ports of Odesa, but Monday's pre-dawn strikes hit infrastructure along the Danube River, a smaller export route that some Ukrainian grain companies have built up as an alternative.

"Warehouses where grain crops were stored were destroyed, tanks for storing other types of cargo were damaged. There was a fire in one of the production premises, which was promptly extinguished," police said in a statement.

News website Reni-Odesa said damaged infrastructure was located at the Reni river port on the Danube and that around 15 drones had taken part in the attack, citing a local official.

Odesa's regional governor, Oleh Kiper, said Russia had attacked with Iranian-made Shahed-136 drones for four hours and that Ukrainian air defences had shot down three incoming drones.

"Russia hit another Ukrainian grain storage overnight," Foreign Minister Dmytro Kuleba wrote on Twitter, without identifying the location of the target.

"It (Russia) tries to extract concessions by holding 400 million people hostage. I urge all nations, particularly those in Africa and Asia who are most affected by rising food prices, to mount a united global response to food terrorism."

(Reporting by Olena Harmash and Valentyn Ogirenko in Kyiv; Writing by Tom Balmforth; Editing by Timothy Heritage)