Five men were remanded into custody on Friday on suspicion of making preparations for a terror attack.
The five were detained on Thursday evening in Kankaanpää, and appeared before the Southwest Finland District court on Friday.
At a press conference on Friday evening, police declined to say whether the men were planning to target a specific community with the attack.
Police said there is no acute danger from the group. All five suspects are under the age of 30 and follow a far-right ideology influenced by accelerationist ideas.
That means they want to foment chaos in society in order to hasten the collapse of western societies, using extreme violence to pursue their aims. Accelerationist ideas have spread online and been cited by several mass killers in recent years.
The men were arrested on Tuesday morning in a joint operation that included Helsinki police and the National Bureau of Investigation (KRP). Four were in Kankaanpää and one was in Tampere at the time of arrest.
Police seized weapons, ammunition and fertiliser that can be used to make explosives.
The Finnish Security Intelligence Service (Supo) and the European Union Agency for Law Enforcement Cooperation (Europol) also participated in the investigation.
The suspects have been charged with the intention to commit terrorist offences and making preparations for a terrorist act under section 6 of the Finnish penal code. They are also being investigated for other crimes, including firearms offences and aggravated theft.
One of the suspects was previously convicted of burglary while two others have been charged with assault in the past.
Police have been following the movements of the group for the past few years. The men first came under the radar when they were suspected of an aggravated firearms offence in 2019 after they were found to have multiple firearms, cartridges and explosives in their possession.
According to police, this is the first instance of a suspected terror offence involving the extreme right in Finland.
Data from Supo indicates that far-right terrorism is a rising threat across Europe, and the idealogy associated with the movement has gained popularity in Finland in recent years.
"This is a concrete example of the significant threat posed by small groups motivated by far-right ideology," Eero Pietilä of Supo stated at a press conference on Friday.
He said that police had not uncovered links to other far-right groups, and the members would not be seen at demonstrations, for example.