Britain's banks, energy and water companies are all said to be on high alert against the threat of a possible Russian cyber-attack amid an escalating diplomatic row between the two countries over the poisoning of a former Russian double agent on British soil.
Fears that Moscow could target Britain's critical national infrastructure came as Russia's ambassador to the European Union (EU) suggested a UK research laboratory could be the source of the deadly nerve agent used in the attack on Sergei Skripal and his daughter Yulia.
"When you have a nerve agent or whatever, you check it against certain samples that you retain in your laboratories. And Porton Down, as we now all know, is the largest military facility in the United Kingdom that has been dealing with chemical weapons research. And it's actually only eight miles from Salisbury," Vladimir Chizhov told the BBC.
He stressed that Russia had "nothing to do" with the poisoning and that it did not stockpile the poison. Chizhov's comments came as a Russian foreign ministry spokesperson also tried to lay the blame on Britain, saying the UK was one of the most likely sources of the nerve agent, along with the Czech Republic, Slovakia, Sweden or possibly the US.
Meanwhile, officers from Britain's Special Branch of intelligence and security services are investigating death threats against another Russian dissident living in the UK, who has received a series of threatening emails linking his fate to Skripal.
Valery Morozov, 63, who claimed political asylum in the UK after blowing the whistle on Kremlin corruption, received a series of emails last week, warning: "They came for Sergei, they will come for you."
According to 'The Sunday Times', Morozov received threats from an anonymous encrypted email address and immediately reported them to Surrey police. When he did not reply, Morozov received a second email, warning: "Do you not care what will happen to you? Waiting for your confirmation."
Scotland Yard has issued a renewed appeal for information from anyone who may have seen a burgundy red BMW owned by 66-year-old Skripal, the former Russian spy who was found unconscious on March 4 in Salisbury along with his daughter, Yulia. The pair remain critical but stable in hospital.
British Prime Minister Theresa May informed Parliament earlier this week that the poison has been identified as being part of a group of military-grade nerve agents known as Novichok developed by the former Soviet Union.
Soon after she announced the expulsion of 23 Russian diplomats identified as "undeclared intelligence officers", the Kremlin expelled the same number based in Russia and also announced the closure of the British Consulate-General in St Petersburg as well as the British Council in Moscow.
Today, the UK government said that independent investigators from the Organisation for the Prohibition of Chemical Weapons (OPCW) will arrive in Britain tomorrow to kick off their investigation into the nerve agent used in the attempted assassinations of the Skripals.
The team from The Hague will meet with officials from the Defence Science and Technology Laboratory in Porton Down and the police to discuss the process for collecting samples, including environmental ones.
The Foreign Secretary (Boris Johnson) revealed this morning that we have information indicating that within the last decade, Russia has investigated ways of delivering nerve agents likely for assassination.
"And part of this programme has involved producing and stockpiling quantities of Novichok. This is a violation of the Chemical Weapons Convention," a Foreign and Commonwealth Office (FCO) statement said.
The results of the OPCW investigation are expected to take a minimum of two weeks.
Meanwhile, Johnson is set to meet his EU counterparts and NATO Secretary General Jens Stoltenberg for talks in Brussels tomorrow to deliberate on joint action against Russia.