The Czech Republic is expelling 18 Russian diplomats after authorities suspect Russia is responsible for a 2014 blast which left two workers dead.
Authorities are looking for two men who were in the country at the time of the explosion under the aliases Alexander Petrov and Ruslan Boshirov.
The same men were accused by the United Kingdom over the Salisbury spy poisoning and are allegedly part of a GIU military intelligence unit called 29155.
The unit is of particular interest to western security services as it is suspected of being linked to multiple incidents – including the poisoning of Bulgarian arms dealer Emilian Gebrev in 2015.
Some members are also believed to have taken part in Russia’s annexation of Crimea in 2014.