Two men were arrested over alleged plan to infiltrate lab where Salisbury nerve agent was analysed

The Dutch government expelled two alleged Russian spies this year after they were accused of planning to hack into a Swiss chemicals laboratory where novichok nerve agent samples from the Salisbury attack were analysed, it has emerged.

The men were arrested in The Hague this spring as part of an operation involving British, Swiss and Dutch intelligence agencies.

The Swiss daily newspaper Tages-Anzeiger reported that the men were carrying equipment that could be used to break into the Spiez laboratory’s IT network when they were seized.

Isabelle Graber, the head of communications at the Swiss intelligence service, the FIS, said in a statement issued to the Guardian: “The Swiss authorities are aware of the case of Russian spies discovered in The Hague and expelled from the same place.

“The Swiss Federal Intelligence Service (FIS) participated actively in this operation together with its Dutch and British partners. The FIS has thus contributed to the prevention of illegal actions against a critical Swiss infrastructure.”

Sergei Skripal, a former Russian military officer and double agent for MI6, and his daughter, Yulia, were poisoned in Salisbury on 4 March.

The Spiez laboratory, near Berne, subsequently confirmed a British claim that the Skripals had been exposed to the military-grade nerve agent novichok. The laboratory has also been investigating poison gas attacks by the Syrian regime backed by the Kremlin.

It is unclear why the two expelled men were in The Hague, which hosts the headquarters of the Organisation for the Prohibition of Chemical Weapons (OPCW).

The Swiss Federal Office for Civil Protection said in June that the Spiez laboratory had been targeted by hackers said to be from the Russian government-affiliated group Sandworm. It is not clear whether the expulsion of the two spies from the Netherlands was linked.

The Sandworm hackers posed as the laboratory’s organising committee and circulated a document with instructions for a forthcoming conference on chemical weapons in September. They then targeted chemical weapons experts who had been invited to the conference and opened the document.

“Someone posed as the Spiez laboratory,” Kurt Münger, of the Federal Office for Civil Protection, said at the time. “We immediately informed the conference invitees that the document was not ours and pointed to the danger. The laboratory itself has not registered any outflow of data.”

In an interview with the Russian TV channel RT, two men identified as Alexander Petrov and Ruslan Boshirov, who have been accused by the UK government of poisoning the Skripals, admitted they had visited Switzerland on a number of occasions.

Play Video 1:24 Men claiming to be Salisbury novichok attack suspects speak to Russian state TV – video

Petrov, who claims to be in the fitness and nutrition business, but is accused with Boshirov of being a member of the GRU, the Russian military intelligence agency, said: “If memory serves me well, we had just a couple of trips to Switzerland. We spent some time during the new year holidays there. Our trips are not always business-related. We went to Switzerland on holiday. We did have some business trips there as well, but I can’t really remember when it was.”

In a statement, the Russian embassy in Switzerland neither confirmed nor denied the arrests. The embassy called the reports “fabrications” and said it “would not qualify attempts to stir up Russophobic sentiment.”

A Russian foreign ministry spokesperson said the agency did not know who the reports were referring to and called on European officials to release more information.

The Kremlin spokesman Dmitri Peskov said on Friday the suspects’ TV interview showed they had no ties to the Russian state and that the Kremlin had nothing to do with the poisoning in Salisbury.

“It’s also absurd to accuse Russia of lying following the statements made by the two ordinary Russian citizens, as these are ordinary citizens indeed, and they also have no relation to the Russian state,” Peskov said.

The Spiez laboratory “advises national authorities and international organisations in implementing and developing arms control and non-proliferation agreements”, according to its website. It is also “involved in international missions relating to arms control and environmental protection”.

In April Sergei Lavrov, the Russian foreign minister, claimed in public he had received confidential information from the Spiez laboratory that the nerve agent used to poison the Skripals in Britain could be a substance never produced in the Soviet Union or Russia.

He said the documents pointed at a western-designed nerve agent, the so-called BZ substance, as a likely cause of the poisoning, thus excluding Russia’s involvement in the attack. He did not disclose the source of his confidential information but said: “We are asking the OPCW why the information which reflected the conclusions of specialists from the Spiez laboratory was completely omitted from the final document.”

His allegations were later rejected since the BZ substance was only being used in the lab as a counter-sample to novichok.

The role of the OPCW has become a hotly contested diplomatic issue as Russia tries to rebut claims that forces loyal to the president of Syria, Bashar al-Assad, have repeatedly used chemical weapons in Syria. The OPCW has a set number of certified laboratories where experts are empowered to examine suspected chemical weapons samples.

The west and Russia have accused one another of preparing to stage chemical weapons attacks in the Idlib region of Syria. Russia claims the west staged videos of fake Syrian attacks to manufacture justification for reprisals. It is expected that France, the UK and possibly Germany would be involved in any counter-attacks.

Russian officials for more than a week have been claiming camera crews, aided by the White Helmets volunteer civil defence group, are preparing to stage fake chemical attacks.

The Dutch government has declined to comment on the expulsions. Two Russian diplomats were expelled from the Netherlands in the wake of the Salisbury attack in a show of solidarity involving more than 25 countries worldwide.

Meanwhile in the UK, the National Crime Agency has “significantly” stepped up the hunt for dirty money linked to the Putin regime since the Salisbury attack.

“We have put a significantly increased focus on this work”, said Donald Toon, director of the NCA’s economic crime unit. He said the focus was on “illicit assets and the assets of corrupt elites”.

Toon called on private schools to report fees possibly being paid via dirty money, and he said some lawyers and accountants were under criminal investigation for knowingly helping launder money in the UK.

The NCA has increased its estimate of the dirty money flowing through and in the UK from £90bn to hundreds of billions.

Additional reporting by Andrew Roth in Moscow