Ukraine's ministry of renovation and infrastructure said on Thursday the U.N.-brokered Black Sea grain export deal had been halted again because Russia had blocked registration of ships to all Ukrainian ports.

"The Joint Coordination Centre in Istanbul has announced that it is impossible to draw up an inspection plan for June 1 due to another unjustified refusal of the Russian delegation to register the incoming fleet for participation in the Initiative," the ministry said on Facebook.

Russia did not immediately comment on the status of the wartime initiative, intended to provide safe Black Sea grain exports.