Ukraine said any ships heading to Russian ports may be military targets, in a tit-for-tat response to a threat from Moscow that escalates the risk to global food markets from the war.

Since Moscow halted the Black Sea agreement that allowed Ukraine to export part of its large grain harvests via safe-passage corridors, Russia has attacked Ukrainian grain storage facilities and warned that all vessels heading to Ukrainian ports would be considered potential carriers of military hardware starting on Thursday.

Wheat prices soared on Wednesday, jumping further when the Defense Ministry in Kyivsaid any ships heading to ports in Russia and Ukrainian areas occupied by Moscow’s troops were also legitimate targets.

It’s an escalation of the conflict and steps up the impact of Russia’s invasion on global commodity markets — including crucial food supplies. Ukraine’s exports have been severely disrupted by the war as Russia has expanded its share of the global wheat trade. Both are major exporters.

Ukraine has previously attacked Russian ships in the Black Sea, sinking the flagship Moskva cruiser with a Neptune anti-ship missile shortly after Russia launched its full-scale invasion. It also sank a landing ship and damaged another in the port of Berdyansk in March, 2022, and Ukrainian rockets have reached Russia’s main supply line to Crimea, the Kerch Strait bridge.

“The fate of the cruiser Moskva proves that Ukraine’s defense forces have the means necessary to repel Russian aggression at sea,” Ukraine’s Defense Ministry said in the statement.

The Black Sea is also home to a major Russian oil terminal, with more than half a million barrels a day of crude flowing through Novorossiysk, which is also a key grain port. Oil prices were little changed, suggesting the market took a skeptical view of the prospect of disruption.

Russia’s defense capabilities in the northern Black Sea and the Sea of Azov are considerable. They include a fleet of warships, including missile cruisers and radar designed to provide a protective umbrella against attack from the air, as well as the large military base on Crimea at Sevastopol.

The longest range missiles Ukraine has are Harpoons and the Storm Shadows provided by the UK. Both have maximum ranges that fall well short of Novorossiysk, as well as its approaches. That will complicate any Ukrainian efforts to strike tankers en route to — or leaving — the area.

Ukraine also lacks a deployable navy and has been using surface water drones in attacks on Russian naval vessels. Most of those attacks have been thwarted by cannon fire. Failing naval escorts, however, Russian merchant ships would have no such defenses.

Attacks on oil tankers would also carry the risk of environmental disaster, which could trigger an unwanted backlash from the international community.

Russia also has several oil products exports terminals on the Black Sea, with refined fuels shipped out of Novorossiysk, Tuapse about 80 miles to the south east and Taman, which is close to the southern end of the Kerch Bridge linking Russia to the occupied territory of Crimea.

--With assistance from Áine Quinn and Alaric Nightingale.

(Updates with Ukrainian Defense Ministry comment, context, from second paragraph.)