The man who is reported to be in his twenties was shot at Furuset in eastern Oslo with police receiving the call at around 1.23am. The man was then rushed to Oslo University hospital.
"There were several shots fired in the area. The man who is shot is in his 20s. The extent of the injury is still unknown, but he was conscious when he arrived at the hospital," said Tore Solberg at Oslo police.
On Friday morning the man's condition was described as serious but not life-threatening and he is deemed to be stable.
Police had by 11am on Friday not apprehended anyone in connection with the shooting.
"We have no specific suspects yet," said Solberg.
"We have some witness descriptions of the perpetrators. We are now looking for clues at the scene and are interviewing witnesses. We also have several units out searching the area," he added.
Solberg told the Verdens Gang (VG) daily that the police remained in the dark over the events leading up to the shooting. According to witness statements the man could have been shot by one or more assailants.
"It is too early to say anything about the background of the shooting. We are now investigating the matter," Solberg told VG.
The shooting is reported to have taken place outdoors and there were a large number of people gathered at the location.