Belarus expelled a Czech diplomat Friday in a tit-for-tat move amid deteriorating relations between Minsk and European Union nations.

In a statement, the Belarusian Foreign Ministry linked the event to “cultivated bias against Belarus by the Czech authorities.”

The Czech Republic expelled a Belarusian diplomat after announcing on Sept. 8 that it had broken up a spy network in Europe that was controlled by Minsk.

At the time, the Czech intelligence agency, also known as BIS, said in a statement that a team of European agents discovered spies from Belarus’ KGB security agency in several European countries.

Poland announced shortly afterward that it arrested a Belarusian spy. It said it would expel a Belarusian diplomat who “supported the aggressive action of the Belarusian state against Poland.”

While no Polish diplomats were expelled, the Belarusian Foreign Ministry said Friday that it had summoned the head of Poland’s diplomatic mission for “a substantive discussion on the current state of Belarus-Poland relations.”

Belarus has been ruled for more than three decades by authoritarian leader Alexander Lukashenko, a close ally of Russian President Vladimir Putin. Lukashenko allowed Russia to use Belarusian territory as a springboard for Moscow’s full-scale invasion of Ukraine in February 2022 and later authorized the deployment of Russian tactical nuclear missiles.

In September Poland completely closed its border with Belarus, citing concerns about the “Zapad 2025” military exercises taking place in the country with the involvement of Russian troops.