Two “Russian spies” arrested in the Netherlands were reportedly plotting to hack a Swiss lab investigating the Salisbury poisoning.
The men are believed to have been agents for the Russian military intelligence service, according to Swiss and Dutch media.
They were reportedly detained earlier this year and kicked out of the Netherlands.
“The Swiss authorities are aware of the case of Russian spies discovered in The Hague and expelled from the same place,” said a spokeswoman for Switzerland’s intelligence service (FIS).
Isabelle Graber said FIS agents had “participated actively in this operation together with its Dutch and British partners”.
She said the pair had attempted “illegal actions against a critical Swiss infrastructure” but did not name the target.
Swiss and Dutch media said the men had planned to hack the Spiez laboratory which at the time was analysing novichok samples from the attack on Sergei Skripal and his daughter Yulia.
Tages-Anzeiger newspaper reported that the men were carrying equipment that could be used to break into the lab’s IT network when they were arrested.
The lab had also been investigating data related to poison gas attacks in Syria.
Switzerland’s foreign ministry said it had summoned Russia’s ambassador on Friday to “protest against this attempted attack” and demanded Russia “immediately” stop any spying in Switzerland.
“We have had indications that we have been in the crosshairs of hackers in the last few months,” said a spokesman for the lab, Andreas Bucher.
He said no data had been stolen.
The Dutch defence department declined to comment.
Russian Foreign Minister Sergei Lavrov dismissed the reports, saying he could not believe the arrests would not have been picked up by the media at the time.
Stanislav Smirnov, a spokesman for the Russian embassy in Switzerland, also shrugged off the claims, reported Russian state news agency Tass.
“We believe that this is a new anti-Russian bogus story made up by the Western media,” he said.
“We have seen this article and it gives rise to a lot of questions… It is absurd, just new groundless allegations.”
Last week, British officials identified Alexander Petrov and Ruslan Boshirov as the suspects in March’s novichok attack.
Theresa May said they were GRU intelligence officers and that the attack had been approved “at a senior level of the Russian state”.
Russia’s President Putin said this week that the men caught on CCTV in Salisbury were “civilians”.
A day later, they appeared on television to claim they were only tourists who had visited the city to view its cathedral and nearby Stonehenge.
The Kremlin said on Friday it would “consider” any request by Britain to question the suspects.