They say they prevented a cyber-attack on the OPCW

British and Dutch authorities say they've foiled a Russian plot to hack the global chemical weapons watchdog.

Intelligence agencies in the Netherlands claim to have prevented the cyber-attack on the Organisation for the Prohibition of Chemical Weapons (OPCW) around the time it was looking into the Salisbury nerve agent attack.

Hours after the Dutch and British allegations, the US indicted seven Russian intelligence officers for conspiring to hack computers and steal data in a bid to delegitimise international anti-doping organisations.

The Dutch Ministry of Defence said four alleged Russian agents arrived into the Netherlands on diplomatic passports | Image: Dutch Ministry of Defence

US Justice Department officials say three of the seven Russian military intelligence officials were previously charged by special counsel Robert Mueller.

US Defence Secretary James Mattis has called for Moscow to be held accountable for allegedly targeting the OPCW.

Responding to the claims made, the Russian embassy in London said the allegations were "irresponsible" and that the UK was imparting "crude disinformation".

In a statement, it said: "As is traditional, it is not backed by any proof and is another element in an anti-Russian campaign being conducted by the British government."

The Russian Foreign Ministry accused the west of "spy mania" over the latest allegations.