More than 50 ambulance crews responded to the scene. Doctors provide assistance to everyone in need.'
The Russian special services arrived at the scene but firefighters delayed tackling the blaze until they came.
The US and UK embassies warned two weeks ago about such an attack by 'extremists' at a crowded venue.
They had suggested it would be earlier but warned foreign nationals to stay away from busy venues.
The motive for tonight's shootings is not clear. Crocus City is about 14 miles northwest of the Kremlin, and was tonight staging a concert by group Picnic, a Soviet era rock band.
One woman said: 'We're in Crocus City. We can't leave. There's a fire all around.'
An eyewitness said: 'Nothing was announced at first. We were already lying on the floor between the chairs. They said nothing, absolutely nothing. We just lay there and didn't know what to do.
'We just took our seats [when the shooting started].
We just took our seats [when the shooting started]. It was literally 8 pm,8:05, or 8:10. Shooting started from further away, from above.
'We sat on the very top row. At first everything was ok, it was kind of unclear what it was.
'Then we realised that something was wrong when we noticed that the ticket takers with these walkie-talkies began to run from top to bottom.
'The shooting started all over again, we heard it from above, we were sitting, then we heard it, we started moving all the way down, we realised that they were also shooting below.
'We lay down at the bottom, in the middle, or rather somewhere on the floor, then we realised that all the people were going upstairs, and we started moving up.
'We eventually got out somewhere at the top. We began to go down the escalators. In short, we hid. They were shooting from all sides, just from all of them.
'We lay there, then noticed that people were somehow running down the escalator. We ran after them. There was one girl lying there.'
The US embassy had warned on 8 March: 'The Embassy is monitoring reports that extremists have imminent plans to target large gatherings in Moscow, to include concerts, and U.S. citizens should be advised to avoid large gatherings.'
They had suggested such an atrocity might happen in the next 48 hours, yet nothing did - until now.
People were told to avoid crowds, monitor the local media for updates, and be aware of surroundings.
The British embassy followed with a similar warning.
Moscow mayor Sergei Sobyanain said: 'Today a terrible tragedy occurred in the Crocus City shopping centre.
'My condolences to the loved ones of the victims. He gave orders to provide all necessary assistance to everyone who suffered during the incident.'
