Russian Foreign Minister Sergei Lavrov said on July 4 that Moscow would respond in kind to Bulgaria's expulsion of 70 Russian diplomats.
Russia's Ambassador to Bulgaria Eleonora Mitrofanova said last week she would ask Moscow to close its embassy in Sofia over the expulsions.
Bulgaria said on June 28 that the Russian diplomats had been working against Sofia's interests. They were given until July 3 to leave the country.
The expulsion, which has severely strained diplomatic ties, is the greatest ever number of Russian diplomats expelled by Bulgaria, which has European Union and NATO membership. Bulgaria has strongly backed Western sanctions against Moscow over its invasion of Ukraine.
European countries have expelled hundreds of Russian diplomatic staff since Moscow launched its unprovoked war against Ukraine on February 24. Russia has reciprocated by sending home diplomats from numerous EU countries.