Norwegian police said in an official release that they are investigating the Saturday shooting in the nightclub, called London Pub, as a terror attack.
"Police detained the suspect. The incident is being investigated as a terror attack", the statement read.
Police representative Christian Hatlo noted that the attack may be a hate crime. According to the authorities, the suspect, is a 42-year-old Norwegian of Iranian descent, who is already known to the law enforcement services.
Following the attack, Norwegian security services raised the terror alert, and the country's intel stressed the incident was an act of "Islamist terrorism."
Police received multiple calls about the incident at 1:14 a.m. local time and arrived at the scene just a several minutes later, and managed to apprehend the suspected shooter several minutes after coming to the scene. He was armed with a pistol and and an assault rifle.
The shooting also resulted in the cancellation of the Pride parade in Oslo, which was scheduled on Saturday.