Turkey is restricting some commercial ship traffic into the Black Sea, according to people familiar with the matter, following growing concern from the government over an uptick in Russian and Ukrainian attacks on vessels in the area. The delay effectively limits the flow of vessels into the Black Sea, where a surge in attacks on merchant shipping, including Turkish-owned vessels, has drawn calls from Ankara for greater security. Earlier this week, the Turkish Foreign Ministry said a group of its citizens were injured after drone attacks on two Turkish-owned vessels. The intensifying Russian and Ukrainian attacks have caused concern over supplies from the Black Sea grain region too, helping to push wheat prices to a two-year high in July. ChokepointsThe Bosphorus and Dardanelles straits run through Turkish waters to connect the Black Sea to the Aegean, and are some of the most heavily used waterways in the world.