Ukraine’s grain exports this month have fallen by more than half amid fears Russia’s unprovoked invasion may have a massive impact on food supplies around the world.

Ukraine’s Agriculture Ministry data released on May 12 shows this month’s exports stood at 298,000 tons — 284,000 tons of corn, 8,000 tons of barley, and 6,000 tons of wheat — compared to 667,000 tons of cereals in the same period of May last year.

It did not say how the grain was delivered.

Ukraine, a major grain producer, exported up to 6 million tons of grain a month before Russia invaded the country in February. Most of it, some 4.5 million tons, was exported through seaports.

Ukraine has been forced by Russia’s invasion to export by train via its western border, its small Danube River ports, or the Romanian Black Sea port of Constanta.

On May 2, Ukraine temporarily closed four seaports until the country “regains control over” them.