British Foreign Secretary Boris Johnson has vowed that Britain will respond "robustly" if evidence of state responsibility emerges after a Russian double agent was left fighting for his life following suspected exposure to an unknown substance.
Sergei Skripal, 66, was found unconscious in Salisbury, Wiltshire, along with his 33-year-old daughter Yulia shortly after 4pm on Sunday.
“I can reassure the House that should evidence emerge that implies state responsibility then HM Government will respond appropriately and robustly" says @BorisJohnson #salisbury pic.twitter.com/6YQEaW39Xr— BBC Daily Politics and Sunday Politics (@daily_politics) March 6, 2018
Answering an urgent question in the Commons, Mr Johnson said he wanted to address speculation about the "disturbing" incident.
Noting that the case has "echoes" of the death of Alexander Litvinenko, a Russian dissident who was fatally poisoned in London in 2006, he told MPs: "While it would be wrong to prejudge the investigation, I can reassure the House that should evidence emerge that implies state responsibility, then Her Majesty's Government will respond appropriately and robustly."
Boris Johnson says if Russia is linked to ex-spy collapse in Salisbury, it would be "very difficult to imagine" UK representation at World Cup going ahead in "normal way" https://t.co/CKBulu7bxw pic.twitter.com/JyNoAY6vpT— BBC News (UK) (@BBCNews) March 6, 2018
Mr Johnson said it was clear that Russia is now "in many respects a malign and disruptive force and the UK is in the lead across the world in trying to counteract that activity".
If suspicions about the events in Salisbury prove to be well-founded, the Government may be forced to look again at its sanctions regime, he added.
Health and counter-terrorism specialists are assisting police as they urgently seek to establish the chain of events prior to the pair being taken unwell.
As the inquiry shaped up to be one of the most politically sensitive for years:
Mr Skripal was convicted in 2006 of passing state secrets to MI6 before being given refuge in the UK as part of a spy swap.
The former colonel in Russian military intelligence, who was sentenced to 13 years in prison, was among four convicts who were given pardons and one of two sent to Britain in 2010 in a deal that was said at the time to be the largest exchange since the Cold War.
Mr Rowley confirmed his specialists were supporting the investigation.
He said: "If you look back at other cases like Litvinenko, if necessary we will bring that investigation into the counter-terrorism network. At the moment the key is, though, to get to the bottom of what caused this."
Asked about a series of suspicious Russian-linked deaths in the UK, Mr Rowley added: "There are deaths which attract attention.
"I think we have to remember that Russian exiles are not immortal, they do all die and there can be a tendency for some conspiracy theories.
"But likewise we have to be alive to the fact of state threats as illustrated by the Litvinenko case."
While the incident remains shrouded in mystery, it comes at a time when ties between Russia and the UK are under severe strain.
Former Scotland Yard counter-terror chief Richard Walton said: "The investigation must take its course but if this is state-sponsored terrorism, and it looks entirely possible, then it will have grave consequences for UK-Russia bilateral relations.
"Relations that are already at breaking point. The UK cannot and will not tolerate state-sponsored terrorism of any kind."
Ex-head of Scotland Yard's counter-terrorism command Richard Walton said it is "entirely possible" that the Salisbury incident is "state-sponsored terrorism" and if so will "have grave consequences for UK Russia bi-lateral relations. Relations that are already at breaking point."— Margaret Davis (@MargaretDavisPA) March 6, 2018
A former associate of Mr Litvinenko alleged the incident in Salisbury bears the hallmarks of a state-ordered assassination.
Yuri Felshtinsky said: "Poisoning is the method of choice for the FSB."
Bill Browder, an anti-corruption campaigner, said: "We don't know much, but based on the headlines from yesterday, who the person was, his relationship with the Kremlin, and the circumstances of his collapse, the first operating assumption should be that this was an assassination attempt by the Kremlin against a traitor of Russia."
Igor Sutyagin, who was part of the same swap deal as Mr Skripal and is now a research fellow at RUSI, urged caution.
He told the Associated Press: "There are lots of former security officers that deserted to the West. It is necessary to balance this information."
Kremlin spokesman Dmitry Peskov said Russia did not "have any information" and had not been approached for help in the investigation.
"Moscow is always open to co-operation," he added.