The fire broke out about midnight in the building of the local Macedonian Association, national radio and the news agency TT reported.
"The fire is raging out of control. We do not know how it started," TT quoted the police spokesman Lars Hansson as saying. " It has been very chaotic." The fire was continuing to blaze some two hours later and police said they had indications that more than 50 people could have been killed, TT said.
The fire broke out in a disco in an immigrant cultural centre within the building and many of the dead were believed to be young people. Police said they were unsure if the dead belonged to an immigrant organisation.
"We don't have very much information. Many rescue workers and police are at the site." the police spokesman Age Johansson said.
Several hundred people were believed to have been in the brick building when the fire broke out.
Gothenburg is Sweden's second-largest city, on the country's west coast about 300 miles southwest of Stockholm.
- AP; Reuters,