Russia declared two Bulgarian diplomats personae non grata on Monday, the Russian foreign ministry said, describing the move as a response to Sofia's expulsion last month of two Russian diplomats suspected of spying, according to Reuters.
The ministry said in a statement that Moscow viewed Sofia's move as groundless.
It's noteworthy that NATO member Bulgaria has kicked out three other Russian diplomats over espionage allegations since last October.
It also declined to grant a visa to Russia's incoming defense attache in December. 
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