Police in the Czech Republic are hunting two men whose passports match the names of the two suspects in the Salisbury poisonings.
Czech police said on Saturday that they are searching for two men carrying various passports, including Russian ones under the names Petrov, 41, and Boshirov, 43.
It comes as Czech Prime Minister Andrej Babis said 18 Russian diplomats are being expelled over allegations that Russian intelligence services were involved in an explosion at a Czech ammunition depot in 2014.
The explosion happened on 16 October at a depot in the town of Vrbetice where 50 tonnes of ammunition was being stored. Two men died as a result.
Mr Babis said: "There is well-grounded suspicion about the involvement of officers of the Russian intelligence service GRU... in the explosion of ammunitions depot in the Vrbetice area."
Czech foreign minister Jan Hamacek said 18 Russian embassy staff identified as secret service personnel would be ordered to leave the country within 48 hours.
Petrov and Boshirov denied being Russian operatives or being involved in the Skripals' poisoning in March 2018.
They told Russia Today they were only in Salisbury as tourists to visit the cathedral and nearby Stonehenge.
Police published a detailed photographic account of the men's movements while in the UK.
An Interpol "red notice" and a European warrant have been issued for their arrest should they try to leave Russia.
Czech Police said in a statement that they are looking for "two persons" who "used at least two identities... in connection with the investigations of the circumstances of serious crime".
They said they were in the Czech Republic from 11 to 16 October 2014, "first in Prague, then in the Moravian-Silesian Region and the Zlin Region".
As well as Petrov and Boshirov, they also used Moldovan and Tajikistan passports under the names Nicolai Popa and Ruslan Tabarov, they added.