Russia's Foreign Ministry has declared two Czech diplomats personae non gratae in retaliation to a similar move by Prague several days ago.
The ministry said in a June 15 statement that the Czech ambassador to Russia, Vitezslav Pivonka, had been officially informed that the two Czech diplomats, whose identities were not disclosed, had been ordered to leave Russia along with their family members in two days.
"The ambassador was told that the move is a mirror response to the provocative action by a Prague official, which was undertaken without any grounds," the ministry's statement says.
On June 5, Czech Prime Minister Andrej Babis said that his government had decided to expel the two staffers as a result of the so-called ricin affair, which he said turned out to be a fake incident sparked by an "internal struggle" between embassy staff.
The Russian Embassy called the expulsions an "unfriendly step" that showed Prague is not interested in normalizing already tense relations between the two countries.
The affair stems from Czech media reports that Andrei Konchakov, deputy director of the embassy's Russian Center for Science and Culture, brought ricin from Russia to Prague in mid-March that was meant to be used in a plot to poison Prague Mayor Zdenek Hrib and two other senior municipal officials, Ondrej Kolar and Pavel Novotny.
Moscow at the time denied the reports as "fabrications."
The scandal broke out on April 26 when Respekt, a Czech investigative weekly, published a report quoting unnamed security sources as saying that a suspected Russian intelligence officer traveling on a diplomatic passport had arrived recently in Prague carrying the deadly toxin as part of an alleged poisoning plot.
Czech media last month identified the suspected Russian intelligence operative as Konchakov.
The three Czech officials -- Kolar, Hrib, and Novotny -- were given around-the-clock police protection at time.
All three have taken or supported actions that have angered the Kremlin, including the renaming of the square in front of the Russian Embassy after a slain former Kremlin critic and the removal of a statue of a Soviet-era general.
As possible payback, Moscow is suspected of having a role in a recent wave of cyberattacks in the Czech Republic.
Moscow, suspected in the 2018 poisoning in Britain of former Russian spy Sergei Skripal and his daughter with a nerve agent, has said the alleged poisoning plot against the three Czechs was part of a "disinformation campaign" aimed at discrediting Russia and threatened "serious consequences" to Czech-Russian relations.