"Ethnic-based gang crime can give Norway the same problems that the USA has had with the Mafia. Society, and most of all the immigrants themselves, will be hit hard," said Lien, researcher at NIBR (Norwegian Institute for Urban and Regional Research).

"If we look at youth under the age of 19 charged with crimes in Oslo, immigrants are unfortunately largely overrepresented. In certain Oslo districts - Furuset, Stovner and Gamle Oslo - gang criminality has a grip. Criminal gangs becoming solid organizations is a sign in international research of an incipient mafia structure being built," Lien said.

Lien said that while the reporting of this type of ethnically based crime increases Norwegian skepticism towards immigrants, gang crimes tend to be inwardly focused, with violence taking place within the ethnic community.

Lien said that there is already great concern about the problem within the respective immigrant communities and that authorities should hurry to create constructive cooperation.

"My suggestions for action are to aim crime fighting work more directly at the target group, that is, those who have already started on the path of a criminal career. Furthermore, it is important that recruits meet reaction at once and not after they have carried out a series of crimes," Lien said.

"Last, but absolutely not least, it is important that immigrants' sense of belonging and trust in Norwegian society is strengthened. If the parallel and separate societal development of Norwegian and foreign culture continues I believe this will only strengthen the worrying development," Lien said.