The video, which lasts a minute and a half, shows several individuals withblurred faces and garbled voices, armed with assault rifles and knives.
They appear to be the lobby of the Crocus City Hall concert venue inKrasnogorsk, northwest of the Russian capital, reports BSS.
The attackers fire several bursts of gunfire, numerous inert bodies arestrewn about and a fire can be seen starting in the background.
The video appeared on a Telegram account considered, according to the SITEmonitoring group, to belong to Amaq, the news arm of IS.
The attack, for which IS claimed responsibility on Friday evening, killed atleast 133 people.
It was the deadliest attack claimed by the jihadist group on European soil.
According to the Kremlin, 11 people have been arrested. Among them are thefour presumed perpetrators of the attack, who, according to Moscow, wereheading for Ukraine.
Neither President Vladimir Putin nor the security services (FSB) have accusedthe jihadist group. Kiev has firmly denied any involvement.
The head of the state-run RT media outlet, Margarita Simonyan, posted twovideos of interrogations of two handcuffed suspects. They both admitted tothe attack but did not say who had organised it.
AFP was unable to confirm the veracity of the videos.