Russian authorities say that more than 60 people have died after gunmen opened fire at a concert hall on the outskirts of Moscow. The building then went up in flames.

Russia's investigative committee is calling the incident a terrorist attack, and the extremist group Islamic State has reportedly claimed responsibility.

The attack occurred on Friday evening in the city of Krasnogorsk, northwest of the capital, as people waited for the start of a concert by a popular band.

Russia's health ministry says that 115 people, including five children, have been hospitalized. More than 60 of them are in serious condition and the number of dead could rise.

Some Russian media reported that the gunmen fled the scene in a white vehicle. Security forces are after them, the media added.

Kremlin spokesperson Dmitry Peskov said President Vladimir Putin was immediately informed of the attack and has since been giving necessary instructions.

The Ukrainian side, where Russia's military invasion continues, denies any involvement.

The Amaq news agency, linked to the Islamic State extremist group, quoted sources as saying that the group's fighters attacked a crowd of Christians, "killing and wounding hundreds" of them and severely damaging the building.

News outlets, including The Wall Street Journal, reported that Washington had earlier this month informed Moscow of the potential for extremist attacks.

They attributed the story to US officials.

The United States and Russia have common objectives to eradicate the Islamic State group and have shared information on terrorist threats in the past.

Washington apparently acted in line with what they have been doing against terrorism even though they are gravely at odds with each other over Ukraine.