Sergei Skripal's Mother Asks Police to Declare Her Son Missing - Niece

"Elena Yakovlevna has filed a police report requesting to declare Sergei and his daughter, Yulia Skripal, missing… We hope that investigators will find their location," Viktoria said.

READ MORE: Alleged Third Suspect in Skripal Case Visited Bulgaria in 2015 — Prosecutor

On February 17, The Sunday Times reported that Sergei Skripal had suffered deterioration in his health and was being treated by doctors at home amid fears that he might never fully recover from poisoning. On Monday, Viktoria said she was sure that Sergei Skripal had already died.

On March 4, 2018, Sergei and Yulia Skripal were found unconscious on a bench at a shopping center in Salisbury. London said they were poisoned with a military-grade nerve agent. London accused Moscow of staging the attack, saying it suspected Russian nationals Alexander Petrov and Ruslan Boshirov of performing the attack and of working for the Russian intelligence.

However, Moscow has repeatedly noted that London has not provided any evidence proving Russian role in the poisoning. Petrov and Boshirov, in turn, denied their involvement in the attack in an interview with the RT broadcaster. They said that while they did visit Salisbury in the spring, they had come as tourists, further noting that they were working in the fitness industry.