Wheat prices on the Chicago Stock Exchange jumped 6.5% after the Russian attack on the port of Izmail on the night of 1-2 August.
"Chicago wheat prices jumped 4% following Wednesday's attack and were still up around 2.5% later in the morning, with traders worried anew about a hit to global supplies from driving Ukraine, one of the world's top exporters, off the market," the media writes.
The agency cited an "industry source" who confirmed that the level of damage at the port of Ismail was "serious".
Analysts also report that grain exports from Ukraine decreased by 40% for the month compared to June as of 1 August due to the breakdown of the grain deal, the agency says.
Russia's attack on Izmail means that the Kremlin is "ramping up its use of force to reimpose a [maritime] blockade [of Ukraine]," Reuters writes.
The Danube port, thanks to NATO member Romania, has served as the main alternative route from Ukraine for grain exports since Russia resumed the de facto blockade of Ukraine's Black Sea ports in mid-July.
However, Russia has been relentlessly attacking Ukraine's agricultural and port infrastructure for over two weeks after refusing to extend a deal that lifted its wartime blockade of Ukrainian ports last year.
Russian drones struck Ukraine's Danube ports in the end of July, destroying a grain storage point. Ukrainian officials said Moscow had struck 26 port facilities, five civilian ships and 180,000 tonnes of grain in nine days of strikes since Russia's withdrawal from the grain deal.
Moscow says it will consider ships bound for Ukrainian seaports as potential military targets.