HELSINKI — Finnish police say they have arrested two Iraqi brothers believed to have been members of the Islamic State group in Iraq and suspected of fatally shooting "11 unarmed and defenseless prisoners" in June 2014.

The National Bureau of Investigation says the men arrived in Finland in September and were arrested Tuesday following an investigation with Finnish security police. In Thursday's statement, the agency said IS posted a video online of the shooting of the prisoners in Tikrit. No further details were given.

Police said both brothers were 23 but did not say whether they were twins. It was unclear whether the men are asylum-seekers. Some 17,000 Iraqis have sought asylum in Finland so far this year.

Associated Press reporter Jari Tanner in Tallinn, Estonia, contributed to this report.