Gunmen launch deadly attack at Moscow concert hall

A massive blaze is seen over the Crocus City Hall on the western edge of Moscow, Russia (Sergei Vedyashkin/Moscow News Agency via AP)

Several gunmen have burst into a big concert hall on the edge of Moscow and sprayed visitors with automatic gunfire, injuring an unspecified number of people and starting a massive blaze in an apparent terror attack.

It comes days after President Vladimir Putin cemented his grip on the country in a highly orchestrated electoral landslide.