Concerns are growing over the possibility of a global food crisis due to the Russian blockade of grain exports from Ukrainian ports as the invasion continues.

The president of a grain exporter in the southern Ukrainian city of Odesa, which is home to the country's largest port, has told NHK that the volume of exports has fallen to around 10 percent of the usual level.

Alexander Polishchenko said his firm has exported wheat and other grains on container vessels to over 50 countries, including Japan.

Polishchenko said the Russian military had been conducting exercises involving missile launches in the Black Sea several months before the start of the invasion.

He told NHK that since the invasion began on February 24, about seven to 15 Russian vessels had gathered around the port, bringing port functions to a halt.

He said all the vessels in the port were barred from leaving. He added vessels that tried to set sail were bombarded or seized by Russian military vessels, with some towed to a port in Crimea.

Polishchenko said his firm has suspended direct exports for a while, and is trying to export goods via foreign ports by first transporting them by truck to countries such as Romania and Poland.

But he said the amount that could be transported would be far short of the level possible by sea, and even if railway transportation is included, it is not a solution.

He added hundreds of tons of wheat that cannot be exported remains in storage, leaving no space to store the next harvest, which is expected to start in about a month.

Polishchenko also said he heard that Russian mines are washing up on the beaches of Odesa almost every week.

He said this is an issue that will remain even after the war ends, suggesting it would not be easy to resume exports after the fighting is over.