The EU's foreign policy chief Josep Borrell called Russia's blockade of key grain exports from Ukraine a "real war crime" on arrival at a EU foreign ministers meeting in Luxembourg on Monday.

"We call on Russia to deblockade the [Ukrainian] ports... It is inconceivable, one cannot imagine that millions of tonnes of wheat remain blocked in Ukraine while in the rest of the world people are suffering hunger," Borrell told reporters.

He accused Russia of weaponizing "the hunger of the people" and said Moscow would have to be held "accountable" for its actions.

Germany pledges support

German Foreign Minister Annalena Baerbock said that Berlin will support Poland and Romania in adapting their rail networks to help bring the millions of tonnes of grain out of Ukraine.

"The railway tracks need to be modernized, we need the right cargo wagons - the German government is working on this with many other actors," she said on arrival at the EU foreign ministers meeting.

"It is clear that, in the end, we will certainly not be able to get out all grain but if we even just manage to free part of it, on various routes, then this will help as we are facing this global challenge."