A total of five of Pohjolan Matka's buses parked at a bus depot in Vantaa were destroyed by an intentionally-set fire early Friday morning.
Due to the spread of the fire, altogether nine buses were damaged in the incident.
According to a post on their website, the Animal Liberation Front said they were behind the arson, in what they described as a protest of the bus company's dealings with the Vantaa-based fur trade auction company Saga Furs.
Pohjolan Matka said the cost of damages to the buses amounted to more than one million euros.
Pohjolan Matka's CEO Johanna Lehtonen said that even though the activist group took responsibility for the crime, other evidence would be needed to confirm it.
Lehtonen would not comment about the company's relationship with Saga Furs, but said she was taken aback by the attack, saying she could not understand why someone would damage other people's property.
"We are grateful that no one was injured," Lehtonen said, adding that five staff members were asleep in the depot building when the fire was set.
It was a windy morning, she said, adding that the fire could have spread even further.
The incident is being investigated as a case of aggravated sabotage by the National Bureau of Investigation.
Television channel MTV3 news first reported that the animal activists claimed responsibility.