Kiev said Tuesday it was expelling a Russian diplomat from the port city of Odessa in response to the "unfriendly" removal of a Ukrainian embassy worker in Moscow.
The announcement came amid heightened tensions between Moscow and Kiev over an uptick in fighting between Ukraine's army and pro-Russia separatists in eastern Ukraine.
It also added to a wave of diplomatic expulsions that have embroiled Russian and European diplomats recently.
The Ukrainian foreign ministry said in a statement that due to "unfriendly actions taken against employees of Ukraine's diplomatic missions" in Russia, Moscow's consul in Odessa had been declared persona non grata.
The envoy was given until the end of the day April 30 to leave the country, the statement added.
The ministry said Russia's decision to expel a Ukrainian diplomat amounted to "the continuation of an anti-Ukrainian campaign" and said it would respond to further action from Moscow.
Ukraine last week had expelled a Russian diplomat in response to Moscow's order for a Ukrainian consul in Russia's second city Saint Petersburg to leave the country.
According to Russia's security agency, the consul was trying to obtain sensitive information from a Russian national.
Recent weeks have seen a wave of expulsions of Russian officials from European countries and the United States over claims of hacking and espionage.
The Czech Republic in particular ordered more than a dozen Russian embassy staff from Prague and several other European countries also removed Moscow's diplomats in solidarity.
Kiev has been fighting pro-Russia separatists in its eastern breakaway regions since 2014, following Moscow's annexation of the Crimean peninsula.
At least 31 Ukrainian soldiers have been killed since the start of the year, compared to 50 in all of 2020, while the separatists say 22 of their fighters have died.