The explosion, thought to be a bomb, sent glass flying across the exclusive Manezh mall as diners in a nearby food hall dived for cover.

Officials say the blast was equal in intensity to that of 300g of TNT.

One survivor Alexander Okropildze told the Reuters news agency: "There was a big bang and smoke. We saw windows fly out."

According to the police, a video game machine exploded spewing glass and metal shards around the game hall.

About a dozen fire trucks and ambulances were dispatched to the mall and the surrounding streets, which usually throng with shoppers and tourists, were cordoned off.

Members of the public, injured by flying glass, were led from the underground centre by emergency crews.

Bloodstained floors

Glass fronts of shops selling expensive imported goods, such as Nike running shoes and fur coats, were shattered and nearby cafes were damaged.

Russian NTV showed a video shot of the inside of the shopping complex minutes after the blast in its evening news bulletin.

The video showed bloodstained floors, broken glass and people being carried out on stretchers.

Ten-year-old Artyom Zamyati, who was in the complex when the blast went off, described himself being jolted and confused. He escaped injury but his mother, who had just come to pick him up, suffered minor cuts on her ear.

Security experts say the blast was most likely caused by a bomb but it has not yet been confirmed.