Protests were taking place against a German coal-powered plant on Friday, with climate activists in Finland also taking aim at the government's involvement in the controversial site.
The Finnish state holds a majority share in Fortum, whose subsidiary Uniper operates the Datteln 4 power plant in the western German state of North Rhine Westphalia.
The plant went online in late May, despite Germany's plans to phase out coal by 2038.
In the Finnish capital Helsinki, about 40 activists from the Extinction Rebellion movement temporarily blocked a street in front of the Finnish parliament.
Helsinki police later tweeted that traffic was running as usual.
Protesters also assembled in front of Finnish state-controlled energy group Fortum's headquarters in Espoo, west of Helsinki.
Greenpeace Finland posted photos of the protest, including of a protester with a placard that read "Money or life, Fortum?" and "Stop Fossil [Fuel] Burning."
German conservationist organization BUND earlier handed over a list signed by over 40,000 people to the Finnish embassy in Berlin, urging Finnish Prime Minister Sanna Marin to quickly move to decommission the plant.
In Datteln itself, police said activists coasted past the plant in around 20 canoes on the adjacent Dortmund-Ems canal. They then held a vigil.
According to the police, up to 30 opponents also took part in a sit-in on a nearby bridge, forcing the closure of a road. The police broke up the meeting and some participants were forcibly carried away. Twenty-five people were given citations.
'Fridays for future'
Representatives of the youth movement Fridays for Future Finland also issued an open letter urging the Marin government to take "urgent action," and close the Datteln 4 plant.
Germany is heavily reliant on coal, which accounts for around a third of the country's energy needs.
The government has earmarked tens of billions of dollars in compensation for energy firms and support for coal-producing regions as part of plans to wind down the coal industry over the coming decades.
Germany currently holds the rotating presidency of the European Union and has vowed to make climate policy a central focus of its tenure.
Next week, Chancellor Angela Merkel is to hold talks with young climate activists in Berlin, including Swedish teenager Greta Thunberg.
Representatives of Fridays for Future will hold an "informal exchange" with the German leader on Thursday on climate issues of national and global importance, government spokesman Steffen Seibert said.
Luisa Neubauer, the 24-year-old face of Fridays for Future's Germany branch, is also expected to attend the meeting.