Dutch intelligence thwarted a Russian cyber attack targeting the global chemical weapons watchdog in April and expelled four Russian agents, the government said Thursday.

The Russians set up a car full of electronic equipment in the car park of a hotel next to the Organisation for the Prohibition for Chemical Weapons in The Hague in a bid to hack its computer system, it said. "The Dutch government finds the involvement of these intelligence operatives extremely worrisome," said Dutch Defence Minister Ank Bijleveld.