Two Russian spies were arrested in the Netherlands in the immediate aftermath of the Salisbury poisonings as they allegedly attempted to hack into the computers of the Swiss laboratory analysing the Soviet-developed Novichok, it has emerged.

The pair were detained in the Hague and extradited back to Russia following an intelligence operation run in conjunction with British, Dutch and Swiss agents.

Their arrest in March is said to have been directly linked to the world-renowned Spiez laboratory near Bern that tested the military-grade nerve agent used in the attempted assassination of former Russia spy Sergei Skripal.

Several sources told Swiss newspapers Tages-Anzeiger and the Tribune de Genève that the pair were arrested on suspicion of preparing to target the lab.

They reportedly had equipment in their possession which would allow them to break into its computer system.

The arrests throw a further spotlight on the two countries to which Mr Skripal’s would-be assassins travelled several times in the months leading up to the attack, increasing suspicions that they could be key locations for Russian agents embroiled in the plot.