A former Russian intelligence officer who was jailed for spying for Britain has been left critically ill after being exposed to an unknown substance in a UK city, according to reports on Monday. Sergei Skripal, 66, was granted refuge in the United Kingdom following a spy swap in 2010 between the United States and Russia, according to the BBC. Mr Skripal and a woman companion, in her 30s, were both critically ill in intensive care on Monday after they fell ill at a shopping centre in the southern city of Salisbury. A passer-by raised the alarm after seeing the pair lying on a bench at the shopping centre. Police said it was “not yet clear if a crime has been committed” but called for witnesses to come forward. Mr Skripal is a retired military intelligence colonel who was jailed for 13 years in 2006 for passing the identities of Russian agents working in Europe to the UK. He was released four years later and moved to the UK. Police in Wiltshire have cordoned off a number of areas across the city and health officials said anyone exposed to the unknown substance had been decontaminated. Teams in protective gear hosed down the street. Neighbours said that police had turned up at Mr Skripal’s house in Salisbury on Sunday evening and had remained there. The case follows the murder in 2006 of Alexander Litvinenko, a former spy and outspoken critic of President Vladimir Putin, who was killed after consuming a radioactive substance in central London following a meeting with two Russians. An official inquiry concluded that the killing was probably ordered by Mr Putin. A separate inquiry has also been hearing evidence in the suspicious death of a Russian whistleblower who collapsed and died after detailing evidence about a huge money laundering scam. An inquest has been examining since last year if financier Alexander Perepilichnyy could have been poisoned by a rare toxin.