Finnish police first announced the raids Tuesday morning via Twitter, and said that the raids were part of a major investigation into the operations of the Bandidos motorcycle club.
The raids were intended to weed out organised crime and illicit drug activity, police said.
Finnish police said they searched clubhouses and homes and have placed seven suspects in custody. The searches also uncovered small amounts of illegal drugs and weapons. Similar raids were carried out in Germany and the Netherlands.
Police have said they won't comment further on the investigation.