Moscow has expelled 20 Czechs in a retaliatory move after Prague sent home 18 Russian diplomats, accusing them of being spies after Czech intelligence linked Russian military agents to a deadly ammunition depot explosion in 2014 that killed two people.
The Foreign Ministry in Moscow said on April 18 that the Czechs affected were told to leave Russia by the end of the day on April 19.
The tit-for-tat move comes as the European Union's top diplomats prepare to meet on April 19 to discuss Russia's alleged involvement in the explosion, an accusation Moscow has called "absurd" and a sign of Washington's influence on Prague.
It also coincides with rising tensions in Ukraine over a massive Russian buildup of troops near its border, and with the United States hitting Moscow with major new sanctions and expelling 10 diplomats.
"A strong protest was declared to the ambassador in connection with the unfriendly act of the Czech authorities against the personnel of the Russian diplomatic mission in Prague," the ministry said in a statement after summoning Czech Ambassador to Russia Vitezslav Pivonka.
Just ahead of the release of the statement, Pivonka was quoted by Russian news agencies as saying he had "just been informed" of the move.
"This is Russia's response," he added as he was leaving the Foreign Ministry..
Czech Prime Minister Andrej Babis said the decision to expel the Russians was made on the basis of "unequivocal evidence" provided by investigators from the Czech intelligence and security services.
Acting Czech Foreign Minister Jan Hamacek said on April 18 in a tweet that the issue will be discussed at a meeting of EU foreign ministers on April 19.
The United States and Britain said they stood in solidarity with the Czech Republic in the dispute, which upset many Czechs who lived for decades under Moscow's dominant rule during the communist era.
"We support our NATO ally the Czech Republic as it tackles and investigates Russia's malign activities on its territory," a NATO official told RFE/RL on April 18.
"This follows a pattern of dangerous behavior by Russia. We express our sympathy to the loved ones of the victims of the explosion in Vrbetice. Those responsible must be brought to justice."
Police in Prague said they had detained seven people on April 18 who are accused of splashing ketchup on the walls of the Russian Embassy in Prague to symbolize the blood of the victims who died in the ammunition-depot explosion.
Hamacek, who is also the interior minister, said that the diplomats who had been identified as intelligence operatives had been ordered to leave the Czech Republic within 48 hours.
The October 16, 2014, blast in Vrbetice, in the eastern Czech region of Zlin, set off 50 metric tons of stored ammunition, killing two people. Two months later, another blast of 13 tons of ammunition occurred at the same site.
The cause of the explosions has never been publicly revealed. It was unclear if there was new intelligence that prompted Czech authorities to make the announcement or why the government decided to move now against the Russians.
Russia's Foreign Ministry said the accusations were yet another example of "hostile" moves by Prague against Moscow, which have included disputes over the renaming of the square in front of the Russian Embassy after slain former Kremlin critic Boris Nemtsov and the removal of a statue of a Soviet-era general from a Prague neighborhood.
"We will take retaliatory measures that will force the authors of this provocation to fully understand their responsibility for destroying the foundation of normal ties between our countries," a Russian Foreign Ministry statement said.
"This hostile move was the continuation of a series of anti-Russian actions undertaken by the Czech Republic in recent years. It's hard not to see the American trace [here]," it said, accusing Prague of "striving to please the United States against the backdrop of recent U.S. sanctions against Russia."
The Czech news magazine Respekt reported that the ammunition and weaponry that was destroyed was intended for Ukraine, which in 2014 was battling Moscow-backed fighters in eastern Ukraine. A Bulgarian arms trader named Emilian Gebrev was reportedly the organizer of the arms deal with Ukraine, Respekt said.
Respekt said investigators last year received new information regarding the explosion, and the government's intelligence committee had discussed the case just two weeks ago.
"Without specific details, I can confirm that international cooperation on this issue is under way, including cooperation with Bulgaria," Hamacek said on Czech TV on April 18.
In his announcement, Babis blamed the blasts on the Russian military intelligence agency known as the GRU, and specifically on a secretive unit known as Unit 29155.
That unit has been linked to a series of attempted assassination plots and other sabotage across Europe, including the 2018 poisoning of Russian former double agent Sergei Skripal in Salisbury, England.
Skipal, a former Russian military intelligence officer, and his daughter Yulia nearly died that March after being exposed to what British authorities later concluded was Novichok, a powerful Soviet-era, military-grade nerve agent. A British woman who accidentally came into contact with the substance died.
Unit 29155 has also been linked to an attack against Gebrev in 2015. Bulgarian officials have said Gebrev, who survived, was targeted with a substance similar to Novichok. In January 2019, they charged three Russians, including a top GRU officer, in absentia in connection with that case.
As part of the government announcement on April 17, Czech police announced they were seeking two suspected Russian agents carrying various passports, including Russian documents, in the names of Aleksandr Petrov and Ruslan Boshirov.
The names match those of the two men that Britain has blamed for the Skripal poisonings.
The open-source-investigation organization Bellingcat identified the suspects as Aleksandr Mishkin and Anatoly Chepiga and said they both worked for Unit 29155.
"The UK stands in full support of our Czech allies, who have exposed the lengths that the GRU will go to in their attempts to conduct dangerous and malign operations -- and highlights a disturbing pattern of behaviour following the attack in Salisbury," British Foreign Minister Dominic Raab said on Twitter.
The president of the Czech Senate, meanwhile, suggested that the explosion could be considered an act of "state terrorism."
"If this is confirmed, we must regard the actions of the Russian secret services as a very serious manifestation of aggression and hostility, which can also be described as an act of state terrorism," Milos Vystrcil, a political opponent and longtime critic of Babis, told reporters. "It is necessary to react clearly, confidently, and harshly on it."
Czech Industry Minister Karel Havlicek said on April 18 that the issue should preclude Russia's Rosatom from taking part in the building of a new nuclear power station in the Czech Republic, or from even taking part in a security review of the project in the run-up to a tender.
Czech security services have warned for years about the risks they say are posed by Russia and China participating in the building of a new block at the Dukovany nuclear power plant.
Earlier this year, political parties agreed on excluding Chinese bidders from the tender while not agreeing on Russian firms for the project, estimated to be worth at least $6 billion.
The Industry Ministry has started a prequalification round for the project, set as a security assessment for potential bidders, before the official launch of the tender, which is expected toward the end of 2021, after a new government takes office following general elections in October.