"Means and forces of the Black Sea Fleet have started monitoring activities of the Spanish navy's Mendez Nunez frigate that entered the Black Sea waters on 17 March", the ministry told reporters.
Last Friday, Spanish frigate the Cristobal Colon entered the Black Sea, prompting the Black Sea Fleet to escort it.
Moscow has repeatedly slammed NATO military manoeuvres in the Black Sea, which, according to Russia, destabilise the situation in the region. Although international agreements allow vessels of other states to cross into the Black Sea and stay there for 21 days, only regional powers should conduct such operations in the area, the Kremlin believes.