The Dutch government has said it disrupted an attempt by Russian intelligence agents to hack the international chemical weapons watchdog as it investigated the Salisbury nerve agent attack.
Four Russians were expelled from the Netherlands after the plan was uncovered in April.
At the time, the Organisation for the Prohibition of Chemical Weapons (OPCW) was working to verify the identity of the substance used in the attack against the former Russian spy, Sergei Skripal, and his daughter, Yulia.
It was also seeking to verify the identity of a substance used in a chemical attack in Douma, Syria.

Four Russians expelled from Netherlands over cyber attack plot targeting chemical weapons watchdog
Authorities say GRU military intelligence agency also behind attacks targeting Porton Down, Foreign Office, MH17 investigation and anti-doping conferenceBritain has accused Russian military intelligence of directing a host of cyberattacks aimed at undermining Western democracies by sowing confusion in everything from sport to transport and the 2016 US presidential election.
"This statement is irresponsible," the embassy said.
The two leaders said they will "defend international institutions from those that seek do to them harm."
They spoke after officials from both countries blamed the GRU for a series of attacks against the international chemical weapons watchdog and other agencies, including the World Anti-Doping Agency and groups investigating the 2014 Malaysian Airlines crash over Ukraine.
Ms May and Mr Rutte said the attacks "demonstrate again the GRU's disregard for the global values and rules that keep us all safe."

Theresa May condemns 'reckless' actions of Russia's spy service service after alleged chemical weapons watchdog cyber attack
Targeting of OPCW 'demonstrates ... disregard for the global values and rules that keep us safe', PM says in joint statement with Dutch counterpartIn a statement issued during a meeting of Nato defense ministers, Mr Stoltenberg said "Nato allies stand in solidarity with the decision by the Dutch and British governments to call out Russia on its blatant attempts to undermine international law and institutions."
He said: "Russia must stop its reckless pattern of behavior, including the use of force against its neighbors, attempted interference in election processes, and widespread disinformation campaigns."
The 29 allies are discussing cybersecurity at talks in Brussels, with the US, Britain, Denmark and the Netherlands due to announce that they will provide offensive cyber-capabilities for use by Nato.

Moscow says US has developed chemical and biological weapons programmes around Russia’s borders
The US has developed a chemical and biological weapons programme around the borders of Russia, according to the Ministry of Defence in MoscowMr Mattis told a news conference that Russia must pay a price and a number of response options were available.
"There was no attack," RIA cited the unnamed source as saying, adding that the allegations stemmed from a Western campaign against Russia.
"We are part of all the organisation's [OPCW's] structures so why would we hack it? We have access, their entire network is open to us. This is another absurdity."
Dutch authorities said they disrupted an attempt in April by Russian intelligence agents to hack the Netherlands-based Organisation for the Prohibition of Chemical Weapons.
Sergei Skripal, a former colonel in the Russian military intelligence, and his daughter Yulia, were found unconscious on a public bench in Salisburyin March.
"If anyone had questions in their mind about Russian military involvement in the Salisbury attacks this will put to rest those doubts," Mr Hunt told the BBC.
"Russian government needs to know that if they flout international law in this way there will be consequences, they will be exposed and people will see the Russian government for what they are - which is an organisation that is trying to foster instability throughout the world."
Prosecutors said the Russians also targeted a Pennsylvania-based nuclear energy company and an international organisation that was investigating chemical weapons in Syria and the poisoning of a former GRU officer.
The indictment said the hacking was often conducted remotely. If that was not successful, the hackers would conduct "on-site" or "close access" hacking operations with trained GRU members travelling with sophisticated equipment to target their victims through wifi networks.
The Labour leader said: "What I said was there was evidence, but the evidence had to be clear, had to be accurate and had to be effective.
He replied: "First of all confront Russia with the evidence, remove any diplomats that clearly are not diplomats and are masquerading as something else and confront Russia with it, but also strengthen international organisations and their protections such as the UN and the Organisation for Prevention of Chemical Warfare.
The two GRU assassins who poisoned Mr Skripal in Salisbury were found to be travelling on fake passports that were three digits apart.
After talks with Nato defense ministers in Brussels, Mr Mattis said: "We are ready today to provide cyber-support to our allies. That is now."
He did not say if the offered capabilities would be used in response to British and Dutch claims that Russia's GRU attempted cyberattacks on the international chemical weapons watchdog and other targets.
But Mr Mattis backed their allegations, saying: "I've seen enough of the evidence to say the Dutch and the British are 100 per cent accurate in who they've attributed this to."
The Organisation for the Prohibition of Chemical Weapons said in a statement that its director general was briefed by Dutch authorities about the Russian hackers who were foiled in April and expelled from the Netherlands.
The OPCW said since early this year it "has observed increased cyber-related activities" and "undertaken measures to mitigate them."
He said: "The Netherlands is the OPCW's host country and, as such, is in charge of ensuring and exercising due diligence in protecting the OPCW headquarters. The OPCW thanks the Netherlands for its actions and will remain in contact in regards to any further developments.
Britain’s defence secretary, Gavin Williamson, branded a series of global cyberattacks blamed on Russia as the reckless actions of a “pariah state,” saying the UK and its Nato allies would uncover such activities in the future.
“Where Russia acts in an indiscriminate and reckless way, where they have done in terms of these cyberattacks, we will be exposing them,” Mr Williamson said at talks in Brussels with the US defence secretary, James Mattis, and their Nato counterparts.
Additional reporting by agencies