Police detained some 55 protesters outside parliament when they broke up a 'convoy' demonstration that had blocked traffic for several hours in pursuit of demands including cheaper petrol and the resignation of the government.
Police began towing vehicles parked on Mannerheimintie when the protesters did not disperse when instructed to do so just after midnight.
Two of the detainees were taken in on suspicion of obstructing an official carrying out his duties, and police tweeted that one of their tow trucks had its tyres punctured with a sharp implement.
The group's demands included the removal of all covid-related restrictions, even though the government has announced it aims to remove them by the middle of this month.
They have said they will continue their protest on Saturday at Citizen's Square, opposite the parliament building.