At least 40 dead and more than 100 injured after gunmen open fire in Moscow

Video posted on social media showed huge plumes of black smoke rising over the building

Smoke rises above the burning Crocus City Hall concert venue outside Moscow, Russia, March 22. Sergei Vedyashkin/Moscow News Agency/Handout via REUTERS

At least 40 people were killed and over 100 hurt when gunmen in camouflage clothing opened fire with automatic weapons on people at a concert in the Crocus City Hall near Moscow on Friday, Russia's FSB security service said.

In one of the worst such attacks in Russia in years, at least five gunmen were shown in unverified videos firing repeatedly at screaming civilians cowering in the concert hall as Soviet-era rock group "Picnic" was about to perform.