More than 60 people have been killed and 145 wounded when camouflage-clad gunmen fired automatic weapons on concertgoers near Moscow with Islamic State claiming responsibility for what was one of the deadliest attacks on Russia in decades.

Gunmen sprayed civilians with bullets just before Soviet-era rock group Picnic was to perform to a full house at the 6200-seat the Crocus City Hall just west of Moscow.

Verified video showed people taking their seats in the hall, then rushing for the exits as repeated gunfire echoed above screams. Other video showed men shooting at groups of people. Some victims lay motionless in pools of blood.

“Suddenly there were bangs behind us – shots. A burst of firing – I do not know what,” one witness, who asked not to be identified by name, told Reuters.

“A stampede began. Everyone ran to the escalator,” the witness said. “Everyone was screaming; everyone was running.”

Raging inferno

Flames leapt into the sky and plumes of black smoke rose above the venue as hundreds of blue lights from emergency vehicles flashed into the night, Reuters pictures and video showed.

Helicopters sought to douse the flames, and around 100 people were evacuated from the basement, Russian media reported. The roof of the venue was collapsing, state news agency RIA said.

Moscow mayor Sergei Sobyanin says a “terrible tragedy” has occurred at the Crocus City Hall. Photo: AAP

It was not immediately clear who the gunmen were. No group has yet claimed responsibility.

Fleet of ambulances

Russian news agencies said 70 ambulance crews had been sent to the scene.

“A terrible tragedy occurred in the shopping centre Crocus City today,” Moscow Mayor Sergei Sobyanin said.

“I am sorry for the loved ones of the victims.”

The shooting began days after President Vladimir Putin was re-elected for a new six-year term and as Russia is prosecuting a war with Ukraine.

Putin has yet to comment in public.

Russia tightened security at airports and stations and across the capital – a vast urban area of more than 21 million people.

Russia’s foreign ministry said it was a “bloody terrorist attack”.

“The entire world community is obliged to condemn this monstrous crime,” Foreign Ministry spokeswoman Maria Zakharova said.

“All efforts are being thrown at saving people.”

In one unverified video posted on social media, men with automatic weapons were shown firing repeatedly at screaming civilians, including women, who were cowering below what looked like an entrance sign to “Crocus City Hall”.

Other video footage showed a number of people lying motionless in pools of blood outside the hall. Another video showed the attackers shooting at people in the concert hall.

The White House said on Friday that images of shooting in the Russian capital were hard to watch.

Ukraine: Don’t blame us

“The images are just horrible and just hard to watch and our thoughts obviously are going to be with the victims of this terrible, terrible shooting attack,” White House spokesman John Kirby said.

The US embassy in Russia warned earlier this month that “extremists” had imminent plans for an attack in Moscow.

Ukrainian presidential adviser Mykhailo Podolyak that Kyiv had nothing to do with the attack.

“Let’s be straight about this: Ukraine had absolutely nothing to do with these events,” Podolyak said in a video message posted on Telegram.

“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.”

—AAP