MOSCOW (AP) — Several gunmen in combat fatigues burst into a big concert hall in Moscow on Friday and fired automatic weapons at the crowd, injuring an unspecified number of people, Russian media said.

Russian news reports said that the assailants also used explosives, causing a massive blaze at the Crocus City Hall on the western edge of Moscow. Video posted on social media showed huge plumes of black smoke rising over the building.

Russia’s state RIA Novosti news agency reported that at least three people in combat fatigues fired weapons. The state Tass news agency also reported the shooting.

Russian media reports said that riot police units were sent to the area as people were being evacuated.