Two "Russian spies" who were arrested in the Netherlands were reportedly planning to hack a Swiss laboratory investigating Salisbury poisoning.
According to the Swiss and Dutch media, the men would have been agents of the Russian military intelligence service.
They were allegedly detained earlier this year and put 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 spokesperson for the Swiss secret service (FIS).
Isabelle Graber said that FIS agents "actively participated in this operation together with her Dutch and British partners".
She said the couple had tried "illegal actions against a critical Swiss infrastructure" but did not name the target.
Swiss and Dutch media said the men planned to hack the Spiez laboratory, which at that time analyzed novichok samples of the attack on Sergei Skripal and his daughter Yulia.
The newspaper Tages-Anzeiger reported that the men had equipment that could be used to break into the lab's network when they were arrested.
The lab also investigated data regarding poison gas attacks in Syria.
The Foreign Ministry of Switzerland said it had called on the Russian ambassador on Friday to "protest against this attempted attack" and demanded that Russia "immediately" stop any espionage in Switzerland.
"We have had indications that we have been in the sight of hackers in recent months," said a spokesman for the laboratory, Andreas Bucher.
He said that no data had been stolen.
The Dutch defense department declined to comment.
The Russian Foreign Minister, Sergei Lavrov, rejected the reports and said he could not believe that the arrests had not been picked up by the media at the time.
Stanislav Smirnov, a spokesman for the Russian embassy in Switzerland, also made the claims, reported the Russian state agency Tass.
"We believe this is a new anti-Russian fake story put together by the Western media," he said.
"We have seen this article and it raises many questions … It is absurd, only new unfounded accusations."
Last week, British officials identified Alexander Petrov and Ruslan Boshirov as the suspects in Novichok's attack in March.
Theresa May said that they were GRU intelligence officers and that the attack had been approved "at a higher level of the Russian state".
Russian President Putin said this week that the men who captured CCTV in Salisbury were "citizens".
A day later they appeared on television to claim that they were only tourists who had visited the city to view the cathedral and nearby Stonehenge.
The Kremlin said on Friday that it would happen "consider" a request from Britain to interrogate the suspects.