The four victims were rushed to the hospital, but the extent of their injuries is not yet known, Oslo police said on Twitter.
Det er 4 menn som er blitt. Kjørt til sykehus med uavklarte skader. Vi har nylig pågrepet 1 mistenkt. Vi har pr. nå ingen flere mistenkte
Norwegian newspaper Verdens Gang reports that the suspected attacker is in his twenties and was previously known to authorities.
The incident sparked panic among patrons of the nightclub. The shooter reportedly fired up to eight times.
Two of the injured are believed to be bouncers at the venue. The shooting reportedly took place after the suspect was asked to leave.
More about: #Norway
