Britain, the United States and Ukraine have been blamed for the Moscow concert hall onslaught which killed at least 139, according to the director of Russia's Federal Security Service (FSB).
Alexander Bortnikov now claims the UK is responsible for the terror attack, despite Moscow initially holding Ukraine accountable, Russian state news outlet TASS reports.
Ukraine has denied Russian accusations they were involved in the attack - which the Islamic State militant group has claimed responsibility for.
The US has said its intelligence indicates ISIS-K - an Afghan branch of IS - was responsible.
Britain, the United States and Ukraine have been blamed for the Moscow concert hall onslaught which killed at least 139GettyRussian officials refused to acknowledge the claims, instead alleging Ukraine had "prepared a window" for attackers to escape the country after the attacks.
US national security council spokesperson Adrienne Watson said Isis bore "sole responsibility for this attack" and "there was no Ukrainian involvement whatsoever".
The fresh accusations from the secretary of Russia's security council that Kyiv was responsible for a deadly attack are "lies", senior Ukrainian presidential aide said on social media.
Mykhailo Podolyak wrote: "The lies are officially spread by (Russian security council secretary Nikolai) Patrushev, and after that by the "head of FSB" (Alexandr) Bortnikov."
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Dalerdzhon Mirzoyev, Saidakrami Rachabalizoda, Shamsidin Fariduni and Muhammadsobir Fayzov, pleaded guilty to committing an act of terror.
Images and videos posted to social media show a string of brutal punishments inflicted on the terror suspects, with one being forced to eat his own ear, and another receiving electric shocks to his genitals.
The four suspects appeared at Moscow's Basmanny district court on Monday.
Mirzoyev and Rachabalizoda both had black eyes, while the latter's ear was heavily bandaged - which appears to be as a result of the beatings issued by Russian security personnel.
Dalerdzhon Mirzoyev, Saidakrami Murodali Rachabalizoda, Shamsidin Fariduni and Muhammadsobir Fayzov appeared in various states of disarray in courtReutersFariduni's face was swollen, while Muhammadsobir Fayzov - who appeared to be missing an eye - made his court appearance in a wheelchair, falling unconscious as he was brought into the dock.
Iranian media, citing IS-Khorasan propaganda network Al Azaim, has since warned Russia that it faces another massacre after the footage began circulating.
The image, which showed a balaklava-wearing terrorist pointing a weapon towards the camera, was accompanied by a lengthy message.
