Britain warned Russia on Tuesday of a robust response if the Kremlin was behind a mysterious illness that has struck down a former double agent convicted of betraying dozens of spies to British intelligence.
Foreign Secretary Boris Johnson named Sergei Skripal, once a colonel in Russia's GRU military intelligence service, and his daughter, Yulia, as the two people who were found unconscious on Sunday on a bench outside a shopping center in southern England.
Skripal, 66, and his 33-year-old daughter were exposed to what police said was an unknown substance in the city of Salisbury. Both are still critically ill in intensive care, police said.