Over 30 people were hit by the spray. No one was seriously injured, however, some of the victims were children.
Helsinki police officer Kari Aaltio said that the attack seemed to be meticulously planned.
“First the perpetrators released smoke over the parade. Then they went around the block and attacked parade participants with the spray. At least two types of gases were used. The perpetrators were dressed in black.”
Police are still looking for several other perpetrators. The suspects come from outside of Helsinki and are Finns. Police are trying to determine if they belong to a larger group.
The men will be kept in custody until at least Tuesday.
An estimated 2,500 people took part in the parade which celebrates gay and lesbian culture.