The activists approached on a boat the wall of the building that adjoins water and made an inscription saying "No need to panic," the Dagens Nyheter newspaper specified. A security guard noticed them soon and reported the incident to the police.
READ MORE: Greenpeace Co-Founder on Ocasio-Cortez's 'Green New Deal': 'Ridiculous Proposal'
The activists aimed at drawing attention to climate issues, which will be on the agenda of the Friday session of the parliament.
Greenpeace has claimed responsibility for the protest action.