The ministry said it acted in response to what it said was the "unmotivated" designation of an employee of Russia's embassy in Moldova as 'persona non grata' on March 19.
Moldova, a small ex-Soviet republic which lies between Ukraine and NATO member Romania, expelled a Russian diplomat over the opening of polling stations for Russia's presidential election in its breakaway region of Transdniestria.
Earlier government statements called Russia's move disrespectful to Moldova's sovereignty. Transdniestria, heavily dependent on Russia for financial support, has no international recognition, not even from Moscow.
Moldova's foreign ministry said on the Telegram messaging app on Friday that it regretted Moscow's decision to expel its embassy employee.
Moldovan authorities "are taking all necessary measures" to prevent attempts to interfere in its internal affairs, it added.
(Reporting by Reuters; Editing by Gareth Jones)
