In solidarity with the Czech Republic, the Baltic states of Estonia, Latvia and Lithuania have expelled a total of four Russian diplomats.
At the request of the foreign ministries in Tallinn, Riga and Vilnius, the employees of the Russian embassies in the capitals of the three EU and NATO states must leave their respective countries within seven days.
The reason given for the move on Friday was solidarity with the Czech Republic, which blames Russian secret services for explosions in an ammunition depot in the east of the country in 2014. Two people died in the explosions.
The Kremlin vehemently denies the accusations.
Prague and Moscow recently expelled each other's diplomats.
Slovakia was the first EU country to expel three Russian diplomats out of solidarity with the Czech Republic for allegedly acting as agents.
The Russian Foreign Ministry announced a reaction to the renewed expulsion of its diplomats.
Representatives of the Baltic states could start thinking about which of them could pack their bags, ministry spokeswoman Maria Zakharova said in Moscow.
Latvian Foreign Minister Edgars Rinkevics tweeted that "Latvia will not tolerate subversive activities on its soil or that of its partners and allies."
Accordingly, the central Baltic state ordered the expulsion of a Russian diplomat who had previously committed violations in Latvia.
Estonia ordered one and Lithuania two embassy staff to leave the country, saying their activities were "incompatible with their diplomatic status."