The video, which lasts a minute and a half, shows several individuals with blurred faces and garbled voices, armed with assault rifles and knives.
They appear to be the lobby of the Crocus City Hall concert venue in Krasnogorsk, northwest of the Russian capital.
The attackers fire several bursts of gunfire, numerous inert bodies are strewn about and a fire can be seen starting in the background.
The video appeared on a Telegram account considered, according to the SITE monitoring group, to belong to Amaq, the news arm of Islamic State.
The attack, for which IS claimed responsibility on Friday evening, killed at least 133 people.
Moscow concert hall attack: 11 suspects detained as death toll climbs to 133
Moscow concert hall attack: 11 suspects detained as death toll climbs to 133
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 the four presumed perpetrators of the attack, who, according to Moscow, were heading for Ukraine.
The head of the state-run RT media outlet, Margarita Simonyan, posted two videos of interrogations of two handcuffed suspects. They both admitted to the attack but did not say who had organised it.
Agence France-Presse was unable to confirm the veracity of the videos.