A British coroner has ruled that he could not hear evidence about the alleged role of the Russian state in the killing of Aleksandr Litvinenko.
The former KGB agent died in London in 2006 from polonium poisoning.
Coroner Robert Owen said on May 17 that the inquest could not hear evidence on the Russian state on grounds of national security.
The ruling means the inquest could be replaced with a public inquiry, which can hear evidence in secret.
In a pre-inquest hearing, Foreign Secretary William Hague asked Owen to prevent some information regarding Litvinenko's death from being revealed during the inquest.
It is thought that Litvinenko was working for Britain's MI6 intelligence service at the time of his death.
Based on reporting by AFP and BBC