Russia has declared two Czech Republic diplomats persona non grata in what it says is a response to an unfriendly move by Prague earlier this month to expel two of Moscow's diplomatic staff.
Russia's foreign ministry said it had summoned the Czech ambassador and told the envoy that the diplomats had by the end of Wednesday to leave the country.
Ties between Moscow and Prague have been strained over disputes about a statue and the renaming of a Czech square as well as reports of a Russian man arriving in Prague and posing a threat to three Czech politicians.
On June 5, Prague expelled two Russian embassy staff members after what Czech Prime Minister Andrej Babis called infighting among embassy personnel which led to false allegations about a planned Russian assault on the Czech politicians.
The politicians, who included the mayor of Prague, were given police protection.
The Russian Embassy in Prague denounced the decision announced by Babis at the time as a "fabricated provocation".
In a statement on Monday, the Russian foreign ministry accused Prague of deliberately trying to escalate tensions with Moscow.