The Mayor of Moscow, Yuri Luzhkov, said on Russian television last night that 29 people had been injured including four children and five were "in a serious state". He called the bombing an "act of vandalism, an act of terrorism" but said he did not want to link it to any event.
The Russian security services have been on alert since Chechen militants were defeated on the battlefield in the southern region of Dagestan last week. The Defence Minister, Igor Sergeyev, warned that they might now resort to terrorism. Mr Luzkhov said last night: "Dagestan comes to mind but... you must have proof."
According to Interfax news agency, the explosion occurred in a video games room on the fourth floor of the Manezh complex. The games room is next to a huge food court, and both are popular hangouts for teenagers.
Television reports said 20 ambulances rushed to the mall, where agents of the Federal Security Service were holding journalists back in case there might be a second blast.
Apart from Muslim extremists, common criminals could equally be behind the blast. Bombs frequently go off in Moscow as different mafia groups settle scores among themselves.
The Manezh complex, with its glass domes, fountains and prancing horses, is associated with Mr Luzhkov, and his team of flamboyant architects. To most Muscovites, it is a museum of consumerism where the prices are unaffordable.
Mayor Luzhkov used to be an ally of President Boris Yeltsin but as elections approach he has gone into opposition and become one of the main rivals of the Kremlin.