Protestors clashed with police during three unauthorized demonstrations on Wednesday, Friday and Saturday of last week which followed the eviction of a group of squatters from a building in Bern on Wednesday.
Police are now asking for witnesses with photo or video evidence of the events to come forward as part of the investigation into criminal behaviour during the events, including damage to property, threats against police and endangering life, Bern cantonal police said in a statement.
Protesters retaliated against police on Wednesday as they proceeded with the eviction of squatters from a property on Effingerstrasse.
Five police officers received medical treatment in hospital after the squatters threw paint pots and firecrackers from the building.
A subsequent protest in the Schützenmatte area of Bern on Saturday evening degenerated into a violent confrontation between protestors and police after police blocked off the path of the demonstration.
Protestors threw missiles at officers, used laser beams to blind them and set up burning barricades. Police responded with tear gas and water cannons.
As a result ten police officers and one protestor were injured.
On Monday an MP of the Swiss People's Party (SVP) lodged a motion calling for a minimum one-year prison sentence for those who commit violence against police officers.
Currently the law stipulates either a fine or a prison sentence.
However the bill was later thrown out by parliament.
Speaking to Le Temps, Bern's director of police and the military Hans-Jürg Käser said it wasn't necessary to toughen penalties, but simply to apply the existing law properly.
Käser said it was unfortunate that, despite 40 people being questioned over the three protests, criminal proceedings had not yet been opened against anyone.