Norwegian black metal, a form of rock music in Norway, has been an influence in world music since the late 20th century. Since the 1990s, Norway's export of black metal, a lo-fi, dark and raw form of heavy metal, has been developed by such bands as Emperor, Darkthrone, Gorgoroth, Mayhem, Burzum and Immortal. More recently, bands such as Enslaved, Kvelertak, Dimmu Borgir and Satyricon have evolved the genre into the present day while still garnering worldwide fans. Controversial events associated with the black metal movement in the early 1990s included several church burnings and two prominent murder cases.