The four abseiled down the side of the building using ropes and attached a banner to the front of the cultural centre.
Police have not made public the message or symbol on the banner, but said the content itself was not illegal. Photographs of the incident published in the Expressen newspaper appear to show the logo of neo-Nazi group Nordic Resistance Movement (NMR), an openly anti-Semitic and racist organization. Several demonstrations by the group over the past year have led to violent clashes.
“I am very disturbed. It's an attack,” one witness, who was eating in the building's restaurant ahead of a theatre performance, told the TT newswire. “At first I thought it was an advert for a show. But then I saw the symbol and understood what it was. It's in the middle of the city and close to the election; my interpretation is that it's an attack on Kulturhuset.”
Security guards at the building reported the incident to police shortly before 6pm on Thursday.
The four perpetrators were discharged after interrogation and identification at the scene, and are suspected of trespassing and illegal flyering. One of the four is also suspected of violent resistance during the apprehension.
Work to remove the banner continued through the evening.
“The police have judged that there's no security risk, so we don't need to cancel any exhibitions or anything. We have chosen to bring in a few more security guards,” said Sofia Cherif, press spokesperson at Kulturhuset Stadsteatern.
She said that for the moment the company had not decided to take any further measures, but would be evaluating the situation fully on Friday.