Wheat and corn prices surged after Russia attacked one of Ukraine’s biggest Danube river ports, ramping up the risks facing Kyiv’s last major grain export route and global food trade.

A drone attack on Monday hit the Danube port of Reni, according to people familiar with the matter, who asked not to be named discussing sensitive information. Ukraine’s southern operational military command earlier said on Facebook that a grain hangar at a Danube port had been ruined, without specifying which one or giving details.

Wheat futures for September delivery settled up 8.6% in Chicago on Monday, by the daily exchange price limit, at $7.5750 per bushel. Corn contracts for December closed up 6% at $5.6825 per bushel, the highest level in nearly a month.