They are declared persona non grata

Russia has expelled several employees of the Bulgarian embassy in Moscow. It all comes as a reaction to the expelling of ten diplomats from the Russian embassy in Bulgaria last month, the Russian Foreign Ministry announced. 

"On April 18, Atanas Krastin, Ambassador Extraordinary and Plenipotentiary of the Republic of Bulgaria to the Russian Federation, was invited to the Russian Foreign Ministry, where he was handed a note declaring employees of the Bulgarian Embassy in Moscow persona non grata," the statement from the ministry reads.