Grain exporters in southern Russia are seeking government assurances that shipments will not be disrupted during the World Cup soccer finals because of tight security on roads and at ports, industry sources said. Local industry players have raised their concerns at talks with regional officials in the city of Rostov-on- Don, which has important grain terminals and will host matches during the tournament starting in June, Reuters reported. They fear restrictions on access to ports and roads could oblige them to decline contracts that would involve grain exports from Rostov-on-Don during the World Cup. "A significant part of the (grain) sector is concerned," a source in the agriculture industry told Reuters. "But there have so far been no instructions from officials on the issue." It is too early to estimate how significant the disruption might be during the month-long tournament, the sources said. Ports on the nearby Azov Sea and the Don River, which runs through Rostov-on-Don, account for about 20 percent of Russia's grain exports per season, officials say. Global commodities merchants Cargill, Bunge and Louis Dreyfus operate terminals in the Rostov area. In the current 2017/18 marketing season ending on June 1, Russia, one of the world's top grain exporters, is expected to supply more than 50 million tons abroad. Islamic State-linked groups have called for attacks on Russia in retaliation for Moscow's involvement in the military campaign against the militant group in Syria. Security services have already started tightening access to passes for ports near Rostov-on-Don, a city of more than 1 million people. Grain harvesting in the Rostov region usually starts in the second half of June. Even if the harvest were delayed until after the World Cup, Russia has a huge carry-over stock of grain ready for export after a record crop last year.