At least four people dressed in camouflage opened fire at the Crocus City Hall, social media video verified by the BBC shows.

Video obtained by Reuters news agency shows a large blaze and smoke rising from the hall.

Russia’s Foreign Ministry described the incident as a “terrorist attack”. Specialist police are at the scene

Footage on social media showed gunmen inside the hallwhile state media reported that some people were still inside.

Tass news agency reported a third of the concert venue is on fire and the roof is almost completely ablaze.

Russian Foreign Ministry spokeswoman Maria Zakharova called on the international community to condemn the incident, which it called “a monstrous crime”.

Eyewitnesses have started to speak to Russian media about the attack. One man, called Vitaly, said he was on a balcony in the hall when he heard shots fired.

“We heard shots, we didn’t know what happened at first. Then I saw some terrorists shooting people,” he said.

“They threw some petrol bombs, everything started burning. We were led out towards an exit.”

An anonymous eyewitness said parents were attending a ballroom dancing competition with their children when the shooting started.

“Children and teenagers were at the competition. People came and said there was shooting. A crush ensued. The children were running out in their ballroom gowns.”

US National Security Council spokesman John Kirby said the images of the shooting were “horrible and hard to watch”.

He added there was “no indication at this time” of Ukraine’s role in the attack.

More than 100 were wounded at the Crocus City Hall, according to the FSB Federal Security Service.

The US says an Islamic State group claim of responsibility is credible. Russia has not commented.

Dramatic video shows panicked concertgoers taking cover as shots and explosions ring out.

A large fire engulfed the roof of the complex and Russia’s national guard is searching for the gunmen.

The White House says it is working to find out more about the situation and Ukraine has denied any involvement in the attack.