Germany, Sweden and Poland on Monday each threw out a Russian diplomat in retaliation for Moscow's expulsion last week of their diplomats for allegedly taking part in protests in support of Kremlin critic Alexei Navalny.
The three EU countries announced the tit-for-tat moves in coordinated statements, drawing an angry response from Russia which accused them of meddling in its internal affairs.
Russia humiliated the European Union on Friday by announcing the expulsions during a rare meeting in Moscow between EU foreign policy chief Josep Borrell and Russian Foreign Minister Sergei Lavrov.
European governments strongly condemned the shock expulsions, with Berlin warning that it would respond in kind.
Moscow's decision to expel the three diplomats "was in no way justified", the German foreign ministry said Monday, adding that the German staff member had been doing his job of "observing developments in Russia by lawful means".
Swedish Foreign Minister Ann Linde said Stockholm had "informed the Russian ambassador that a person from the Russian embassy is asked to leave Sweden".
"This is a clear response to the unacceptable decision to expel a Swedish diplomat who was only performing his duties," she wrote on Twitter.
The Polish foreign ministry likewise condemned the "groundless expulsion" of a Polish diplomat from Saint Petersburg and said it had declared "persona non grata" a Russian consular official in Poznan, western Poland.
The Russian foreign ministry immediately hit back.
"Today's decisions by Poland, Germany and Sweden are unfounded, unfriendly and are a continuation of the very series of actions that the West is taking with regard to our country and which we qualify as interference in our internal affairs," spokeswoman Maria Zakharova said on state channel Rossiya 1.
The Kremlin earlier on Monday defended the expulsion of the EU diplomats during Borrell's high-profile visit, and insisted it remained interested in reviving relations with Brussels.
Kremlin spokesman Dmitry Peskov said the declaration of the three foreign diplomats as personae non gratae was a "consequence of the actions of some diplomatic missions in Moscow against the backdrop of illegal riots".
Peskov added that Moscow did not initiate "the collapse" of the relationship with the EU.
"Russia has been and remains interested in reviving relations between Moscow and Brussels," he told reporters.
Navalny, a fierce critic of President Vladimir Putin, was arrested upon arrival in Moscow on January 17 after spending several months in Germany recovering from a poisoning attack the West believes was ordered by the Kremlin.
He was jailed for nearly three years last week for violating parole conditions while in Germany.
Tens of thousands of Russians have taken to the streets in recent weeks to protest against Putin's 20-year rule and demand Navalny's release, triggering a fierce police crackdown on demonstrators.
Western leaders, too, have called for Navalny to be freed immediately.
Russia has bristled at the international backing for Navalny, accusing Europe and the United States of interfering in its domestic affairs.
The EU's Borrell is expected to meet with foreign ministers from the 27 member states on February 22 to discuss fresh sanctions against Moscow that would require a unanimous vote among the EU members.