At least 93 people were killed in an attack on Friday near Moscow, Russia's Investigative Committee said on Saturday, citing preliminary data, and warned that the number of victims was expected to rise further.
Camouflage-clad gunmen opened fire with automatic weapons at concertgoers near Moscow on Friday in an attack claimed by Islamic State militants.
Flames leapt into the sky and plumes of black smoke rose above the venue, Reuters pictures and video showed.
Russian media reported a second blast at the venue and there were reports that some of the gunmen had barricaded themselves somewhere in the building.
The shooting appeared to have begun at a concert of the band Picnic.
Suddenly there were bangs behind us shots. A burst of firing I do not know what, one witness who asked not to be named told Reuters.
