At least 40 people have been killed after gunmen burst into a concert hall in Moscow and fired at the crowd in an attack claimed by Islamic State.

The gunmen, wearing combat fatigues, also caused a huge blaze at the Crocus City Hall. Russian media reported the venue’s roof was collapsing.

At least 40 people were killed and more than 100 wounded, according to Russia’s FSB security service.

Russian media said children were among the dead, citing a Russian MP. State news agency TASS cited the Moscow region ministry saying 146 people had been wounded.

Islamic State claimed responsibility for the attack on its Telegram channel, Reuters reported.

The attack, which Russian authorities are investigating as terrorism, is Russia’s deadliest in recent years.

In other videos posted by Russian media and Telegram channels, extended rounds of gunfire could be heard while men with rifles moved through the venue’s mall.

Russian news reports said the attackers threw explosives, triggering the massive blaze at the venue, where flames and plumes of black smoke could be seen rising into the air.

Reports said concertgoers were being evacuated but an unknown number could have been trapped by the blaze.

All tickets in the 6,200-seat concert hall for a performance by Soviet-era rock group Picnic had been sold out.

Moscow Mayor Sergei Sobyanin described the attack as a “huge tragedy” and cancelled all mass gatherings scheduled for the weekend.

Russian authorities said security had been tightened at Moscow’s airports and railway stations.

President Vladimir Putin was receiving regular updates about the shooting, Kremlin spokesman Dmitry Peskov said.

Two weeks ago the US embassy in Russia warned “extremists have imminent plans to attack large gatherings in Moscow, to include concerts”.

It issued the warning several hours after the FSB said it had foiled an attack on a synagogue in Moscow by an Islamic State cell.

White House national security adviser John Kirby said he could not yet speak about all the details but that “the images are just horrible. And just hard to watch”.

Mr Kirby said there was “no indication at this time that Ukraine, Ukrainians were involved”.

But Russia said if the US knew for sure Ukraine was not involved then it should share any information it had.

Russian foreign ministry spokeswoman Maria Zakharova said: “On what basis do officials in Washington draw any conclusions in the midst of a tragedy about someone’s innocence?”

She said if Washington had information it should be shared and if it had no information it should not be talking in such a way.

Ukraine’s presidential adviser Mykhailo Podolyak said Kyiv had nothing to do with the attack.

“Let’s be straight about this: Ukraine had absolutely nothing to do with these events,” Mr Podolyak said.

“We have a full-scale, all-out war with the Russian regular army and with the Russian Federation as a country. And
regardless of everything, everything will be decided on the battlefield.”

It comes days after Mr Putin secured his fifth term as Russia’s president in an electoral landslide.

Russia was shaken by a series of deadly terror attacks in the early 2000s as it fought separatists in the Russian province of Chechnya.

In October 2002 Chechen militants took around 800 people hostage at a theatre in Moscow which was stormed by Russian special forces two days later, leaving 129 hostages and 41 Chechen fighters dead, most from the effects of the gas Russian forces used to subdue the attackers.

In September 2004 around 30 Chechen militants seized hundreds of hostages at a school in southern Russia. The siege ended in a bloodbath two days later with more than 330 people, about half of them children, killed.