Spy vs spy

British authorities have new information about the mysterious substance that left a former Russian spy and his daughter in critical condition, the minister responsible for public safety said Wednesday.

Home Secretary Amber Rudd said officials would make a statement later in the day about what sickened Sergei Skripal, 66, and his 33-year-old daughter, Yulia, who were found slumped on a bench in the centre of the southern city of Salisbury on Sunday.

Rudd on Wednesday chaired a meeting of the government's emergency committee, known as Cobra, to consider the investigation, which is now in the hands of counterterrorism police.

"We do know more about the substance and the police will be making a further statement this afternoon in order to share some of that," she said. She added that it is important to respond not to rumour but to evidence.

Her comments came as Moscow said the case was being used to fuel an "anti-Russian campaign" and further strain ties with Britain.

"What happened to Skripal has been immediately used to further incite an anti-Russian campaign in Western media," Russian Foreign Ministry spokeswoman Maria Zakharova said.

Skripal, a former colonel in Russia's GRU military intelligence service, was convicted in 2006 of spying for Britain and imprisoned. He was freed in 2010 as part of a widely publicized spy swap in which the U.S. agreed to hand over 10 members of a Russian sleeper cell found operating in America in return for four Russians convicted of spying for the West.

He and his daughter were found collapsed on a bench near a shopping mall Sunday in the town of Salisbury, 90 miles (145 kilometres) southwest of London. Police believe they were exposed to an unknown substance, and a British military research facility is thought to be conducting tests to determine what it is.

Foreign Secretary Boris Johnson told lawmakers Tuesday that if Moscow is shown to have been involved in the Skripal case, the government would act — possibly downgrading England's participation in this year's soccer World Cup in Russia. Johnson warned British officials may not be involved in the sporting event "in the normal way," but did not elaborate.

British counterterrorism specialists have taken control of Skripal's case from local police trying to unravel the mystery of what happened. The matter has not been declared a terrorist incident.

Authorities have cordoned off a new scene in the case, securing Solstice Park, a business park in Amesbury near Stonehenge, the prehistoric monument and world heritage site. Amesbury is about nine miles from Salisbury.

Police also asked members of the public to come forward if they had visited Salisbury's centre, a pizza restaurant or a pub where the pair were last seen on Sunday.

As speculation swirled, experts watching the matter say the circumstances so far suggest that it is unlikely that a radioactive substance was responsible, as was the case with Litvinenko.