BRUSSELS — Two Russian spies caught in the Netherlands and expelled had been plotting cyber sabotage of a Swiss defense laboratory analyzing the nerve agent used to poison a former Russian agent in Britain, Swiss officials said Friday.

The story — first reported by the Dutch newspaper NRC and the Swiss newspaper Tages-Anzeiger, and confirmed by Swiss officials — adds a new dimension to the charges by Western governments that the Kremlin is waging a sophisticated and unconventional campaign to work its will abroad, and undermine adversaries and their alliances.

Britain contends that Russia sent two other spies to a quaint English cathedral city in March, carrying a military-grade poison to assassinate a turncoat former colleague, Sergei V. Skripal, which the Kremlin denies. The two men, publicly identified and charged by the British authorities, appeared on Russian television on Thursday to deny involvement in the poisoning that sickened Mr. Skripal and three others, and killed one person, insisting that they were sports nutritionists, not spies.

The Dutch authorities declined to comment on any expulsion of Russians or any plans for a cyber attack. The Swiss described the events as having taken place “earlier this year” but declined to be more specific. It was not clear if the Russians were among the diplomatic employees — many suspected of being intelligence agents — expelled by Western governments in retaliation for the Skripal attack.