A former spy is in critical condition after coming into contact with an "unknown substance" in the British city of Salisbury, British media reported.
Officials have not yet released the man's identity, but British media say he is 66-year-old Sergei Skripal, who was convicted in 2006 of spying for Britain's MI6 intelligence agency.
He was sentenced in Moscow to 13 years in prison and was released in 2013 in a US-Russian spy swap.
His identity was first announced by the BBC.
After his arrest in Moscow in 2004, Skripal admitted that he was recruited by the British intelligence service in 1995, and that he gave them information about Russian agents in Europe, and that he received a fee of $100.000 in return.
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