A series of incidents occurred, particularly on Friday night, in which groups of young men attacked individuals unprovoked, news agency NTB and Aftenposten reported.
Of a total of 20 violent incidents in the capital on Friday night, a significant number — higher than the average incidence — were unprovoked, Aftenposten writes.
“There was an above-average number of disturbances and fights during the night,” Oslo Police operation leader Tor Jøkling told NTB on Saturday.
Between 11pm on Friday and 2:30am Saturday, around 20 violent incidents occurred in and around the city of which a high proportion were unprovoked, the police officer confirmed.
“There is much to suggest that this is related to large groups of men who are carrying out unprovoked attacks on individuals or smaller groups,” Jøkling said.
The suspected culprits are described as “of foreign origin and appear to be in their late teens” in NTB’s report.
Victims were “mildly to moderately injured”, the news agency writes.
“It’s clear that we are taking this seriously. People should be able to go out and have a good time without fearing unprovoked violence,” Jøkling added.
A number of suspects were detained by police and some were released, while others had already disappeared from the scene of incidents when police arrived.
The majority of the assaults occurred in the centre of the city, including around the Olav Vs Gate street and areas where bars and other nightlife establishments are concentrated, police confirmed.
Although the number of incidents was higher than usual, they are not thought to have been planned, police operation leader Tor Grøttum told Aftenposten.
“There is nothing to suggest (that they were planned). Friday and Saturday nights are the busiest shifts for us, but this weekend saw a remarkable number of incidents,” Grøttum said.
The “offensive demeanour and behaviour” of the culprits suggested that they had been in fights before, he also said.
“We encourage anyone who witnesses violent incidents or conflicts to contact the police,” Grøttum told Aftenposten.