A Russian dissident who became a British citizen, Mr Litvinenko died aged 43 in November 2006, three weeks after he drank tea laced with radioactive polonium-210.
A public inquiry concluded in 2016 that the killing of Mr Litvinenko, a critic of Vladimir Putin, had “probably” been carried out with the approval of the Russian president.
As Sergei Skripal, 66, fought for his life after being found unconscious on a bench, Marina Litvinenko said: “It’s like deja vu, (like) what happened to me 11 years ago.”
She added: “In Russia it is still (an) old-fashioned and old-style KGB system… It’s still all the same. If there is an order to kill somebody it will happen.”
The Litvinenko inquiry found two Russian men – Andrei Lugovoi and Dmitri Kovtun – had deliberately –poisoned their victim, leading to an agonising death.
It said the use of the radioactive substance was a “strong indicator” of state involvement and that the two men had probably been acting under the direction of the FSB, Russia’s state agency.
Possible motives included Mr Litvinenko’s work for British intelligence agencies, his criticism of the FSB, and his association with other Russian dissidents, while it was said there was also a “personal dimension” to the antagonism between him and Mr Putin.