A tourist boat floats on the Moskva river in front of the Kremlin in downtown Moscow on Dec 9, 2019. (DIMITAR DILKOFF / AFP)

MOSCOW - Russia declared two Bulgarian diplomats personae non grata on Monday, the Russian foreign ministry said, describing the move as a response to Bulgaria’s expulsion last month of two Russian diplomats suspected of spying.

The ministry said in statement that Moscow viewed Bulgaria’s move as groundless.

NATO member Bulgaria, which usually maintains good ties with Russia, has kicked out three other Russian diplomats over espionage allegations since last October. It also declined to grant a visa to Russia’s incoming defence attache in December.

Also on Monday, the Russian foreign ministry summoned Bulgaria's ambassador in connection with the expulsion of two Russian diplomats from Bulgaria last month, the RIA news agency reported.

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Moscow had promised retaliatory measures after the diplomats were declared ‘personae non gratae’. RIA showed footage of the ambassador arriving at the ministry.