Two Russians agents were arrested and expelled from the Netherlands earlier this year, suspected of trying to spy on the lab where samples of the poison used on Sergei Skripal were being tested, according to reports. 

Switzerland’s Tages Anzeiger newspaper said Swiss, Dutch and British authorities had worked together to foil the plot directed at the Spiez laboratory near Bern, where experts in nuclear, biological and chemical weapons work.

The paper cited the Swiss NDB intelligence agency as confirming the information it and the Dutch NRC Handelsblad had gathered.

The NDB did not immediately respond to an email from Reuters seeking comment.

The lab has analysed suspected poison gas deployed in Syria and samples of the Novichok nerve agent that Britain accused Russia of using to try to murder former spy Sergei Skripal and his daughter.

But the paper said the two suspects were not the same men accused of carrying out the attack in Salisbury in March.

On Friday the Kremlin-backed RT news channel aired an interview with Alexander Petrov and Ruslan Boshirov, who the UK government say carried out the assassination attempt.

During the bizarre exchange the pair insisted they were merely tourists, despite embarking on a brief 48-hour international trip during which they travelled to Salisbury from London on two consecutive days – one of which was the day the Skripals were poisoned.