KYIV, July 20 (Reuters) - Ukraine's Defence Ministry said on Thursday it would consider all ships travelling to Russian ports and Ukrainian ports on the Black Sea that are occupied by Moscow as potential carriers of military cargo from July 21.

A day after Russia said that any ships travelling to Ukraine's Black Sea ports will be seen as possibly carrying military cargoes, the Ukrainian defence ministry said it could repel what it called Russian aggression at sea.

"The fate of the cruiser 'Moskva' proves that the Defence Forces of Ukraine have the necessary means to repel Russian aggression at sea," the ministry said, referring to the flagship of Russia's Black Sea Fleet which was sunk last year.

"Ukraine's Ministry of Defence warns that from 00:00 on July 21, 2023 (2100 GMT on Thursday) all vessels heading in Black Sea waters in the direction of the Russian Federation's seaports and Ukrainian seaports on Ukrainian territory temporarily occupied by Russia may be considered by Ukraine as carrying military cargo with all the relevant risks."

Russia this week quit the Black Sea Grain Initiative that was brokered by the United Nations and Turkey a year ago and allowed safe Black Sea shipments of Ukrainian grain, and revoked guarantees of safe navigation.

Ukrainian officials want to continue the Black Sea grain shipments and are trying to establish a temporary route.

The Ukrainian Defence Ministry also said that navigation in the northeastern part of the Black Sea and the Kerch-Yenikal Strait of Ukraine was banned as dangerous from 05:00 a.m. (0200 GMT) on July 20.