Moscow on Wednesday expelled seven European diplomats after their countries ordered Russian diplomats to leave in solidarity with the Czech Republic, which is engulfed in a diplomatic row with Russia.
The Czech government this month accused Russian security services of being behind a deadly explosion at an arms depot in eastern Czech Republic in 2014.
It expelled a number of Russian diplomats over the allegations, with Slovakia and the Baltic states of Estonia, Latvia and Lithuania following suit in solidarity.
Russia's foreign ministry on Wednesday said in a statement that a total of four diplomats from Estonia, Latvia and Lithuania have been declared "persona non grata" and must leave the country within seven days.
It added that the Baltic states "continue to conduct an openly hostile course towards our country, in this case hiding behind pseudo-solidarity with the indiscriminate actions of the Czech Republic towards Russia."
Lithuania's foreign ministry said in a statement that its embassy's expelled employees have never engaged in activities incompatible with the duties of a diplomat.
It added that it hopes "Russia will change its course of aggressive foreign policy, stop blaming other states for the escalation of the situation and finally hear signals sent by the countries of the Western community."
In a separate statement on Wednesday, the Russian Foreign Ministry also announced the expulsion of three Slovak diplomats, who must leave by May 5, and accused Bratislava of "false solidarity" with Prague.
Slovakia's actions "damage the traditionally friendly Russian-Slovak relations and constructive bilateral cooperation," the statement added.
The expulsions come as Russia's ties with the West have deteriorated to Cold War levels, with a number of European countries recently kicking out Russian diplomats over allegations of espionage.
In the latest scandal, Prague this month said Czech police were seeking two men in connection with the arms depot blast, and expelled 18 Russian diplomats over the spy allegations.
The wanted men were also identified as suspects in the 2018 poisoning of former Russian double agent Sergei Skripal and his daughter in the English town of Salisbury in 2018.
Moscow retaliated by kicking out 20 Czech embassy staff and both sides imposed a ceiling on embassy workers, meaning dozens more will have to leave by next month.
The Czech Republic also asked its partners in the European Union and NATO to expel Russian diplomats in solidarity.
Slovakia, which formed a single country with the Czech Republic until 1993, expelled three Russian diplomats, while the Baltic states, which were once part of the Soviet Union, ordered four Russian diplomats to return to Moscow.