Police in the Pirkanmaa or Tampere region detained the man in question last Friday evening on suspicion of having committed war crimes.
The local district court remanded the man into custody Monday afternoon following an application by the National Bureau of Investigation. Reports so far indicate that investigations are focusing on incidents that occurred in Iraq in spring 2014.
"It happened in a situation where there was armed conflict between different sides," said NBI’s lead investigator Jari Räty.
Detective Chief Inspector Räty said that with the investigation still underway, he did not want to divulge details about the case.
"There weren’t many victims in this isolated crime. We received information about the events and the suspect quite recently – at the end of last week. The suspect was in the Pirkanmaa area and we later detained him."
NBI takes over from local police
Police did not offer any comment on whether or not the detainee had any links with the extreme Islamist group Isis. Räty however stressed that the case had no connection with the terror attacks in Paris last Friday.
The National Board of Investigation has taken over responsibility for investigating the case from the central Finland police. Officers are said to be in close contact with the security and intelligence police Supo as well as with foreign officials.
"We are in the early stages. We have several lines of investigation open," Räty said.