Sergei Skripal, a former colonel in Russian military intelligence who betrayed dozens of agents to Britain's MI6 foreign spy service, and his daughter Yulia, were found unconscious on a public bench in the southern city of Salisbury on March 4.
NATO Secretary-General Jens Stoltenberg said in a statement Moscow's behaviour is "destabilising and dangerous," while allies in the West condemned the nerve agent attack and called on Russia to "address all questions" related to the issue.