Russia is putting the world at risk of famine through its blockade of Ukraine's shipments of grains and restrictions on its own exports, according to EU foreign policy chief Josep Borrell.

The threat to food security — and a "battle of narrative" with Russia concerning Western-imposed sanctions on Moscow over Ukraine — will dominate the upcoming European Union foreign ministers' talks in Luxembourg.

"We are ready to work with the UN and our partners to prevent any unwanted impact on global food security," Mr Borrell said in an article published on his official blog.

"Russia's conscious political choice is to 'weaponise' grain exports and 'use them as a tool for blackmail against anyone [who] opposes its aggression' in Ukraine," Mr Borrell said.

He said Russia had turned the Black Sea "into a war zone, blocking shipments of grain and fertiliser from Ukraine but also affecting Russian merchant shipping".

"Russia is also applying quotas and taxes on its grain exports," he added.

The sanctions imposed by the EU "do not prohibit Russia to export any agricultural goods, payment for such Russian exports or the provision of seeds, provided that sanctioned individuals or entities are not involved".

He added that it was imperative for Ukrainian exports be allowed to resume by ship.

"We are working closely with the UN on this issue and the EU and its member states are ready to do their part of the necessary actions to achieve this," he said. "We hope that a solution can be found in the coming days. Not doing this threatens to cause a global food catastrophe."

Ukraine accuses Russia of stealing grain

While the ongoing war in Ukraine has made it increasingly difficult for the country to export its major crop, Ukraine has also accused Russia of outright theft of grain from the territories where Russian forces are occupying.

Aerial images collected by US satellite imagery company Maxar appear to show Russian-flagged ships carrying grain harvested in Ukraine and transporting it to Syria, a close ally of Russia.

Two Russian-flagged bulk carrier ships that docked in the Russian-controlled Crimean port of Sevastopol in May were pictured being loaded with grain.

Days later, Maxar satellites collected images of the same ships docked in Syria, with their hatches open and trucks lined-up, ready to haul the grain away.

Speaking at the St Petersburg International Economic Forum, Russian president Vladimir Putin said that, while Russia could "significantly increase its export of food and fertiliser", he expressed concern that Ukraine might use income from exports to pay for weapons.

Despite Mr Putin's claims and apparent shipments to allies such as Syria, Russian grain isn't getting out into the global market either, with Moscow placing the blame on a sweep of international sanctions against Russian banking and shipping industries.

ABC/Wires