The suspects of the 2018 novichok nerve agent poisoning of Sergei and Yulia Skripal in Salisbury, England, have been linked to a 2014 blast in the Czech Republic that killed two people.
The Czech Republic announced Saturday that it was expelling 18 Russian diplomats who it has identified as spies in a case related to a huge ammunition depot explosion in 2014.
Police officers in the Czech Republic seek two Russian nationals who used passports registered to Alexander Petrov and Ruslan Boshirov.
Prime Minister Andrej Babis said the move is based on "unequivocal evidence" provided by the Czech intelligence and security services that points to the involvement of Russian military agents in the massive explosion in an eastern town that killed "two innocent fathers". They and Moscow both denied involvement.
The pair then switched to one Moldovan passport in the name of Nicolai Popa, born July 18, 1979 and a Tajikistan passport in the name of Ruslan Tabarov, born October 23, 1975.
Interior Minister Jan Hamacek, who is also serving as the foreign minister, said the Russian embassy staffers were clearly identified as Russian military spies.
According to Czech police they were first in Prague, and later in the Morovian-Silesian region and then finally in the Zlin region.
"There is a reasonable suspicion that Russian secret agents of the GRU service were involved in the 2014 explosions of an ammunition dump in the Czech village of Vrbětice", he said.
The Czech Republic "has apparently made a decision to close its embassy in Moscow" by expelling 18 Russian diplomats, the Interfax news agency quoted an unnamed diplomatic source as saying on Saturday.
United Kingdom authorities believe the two Russians are responsible for the Salisbury attack. Now Czech authorities believe the same men were involved in the bombing of a warehouse in Vrbetice, in the east of the country. "I will also speak about it at the European Union foreign ministers meeting on Monday", Hamacek tweeted.
"We're in a similar situation to Britain in the attempted poisoning case in Salisbury", added Hamacek.
Russian Federation denied involvement but some 300 diplomats were sent home in subsequent tit-for-tat expulsions.
The US said it was expelling 10 diplomats from the Russian Embassy in Washington DC on Thursday in response to a cyber-attack as well as other Russian activities.