A Finnish court on Friday jailed 23-year-old twin brothers from Iraq for four months pending trial on suspicions they were Islamic State militants who fatally shot 11 unarmed soldiers in Iraq in June 2014.

Friday's custody hearing was held behind closed doors at the Pirkanmaa District Court in Tampere.

The two were arrested Tuesday at a refugee center in the town of Forssa, 120 kilometers (75 miles) northwest of capital of Helsinki. Finnish police say an IS video shows the men taking part in a massacre outside the Iraqi city of Tikrit.

The killing of the 11 Iraqi soldiers was part of atrocities committed by IS in the Camp Speicher military base outside Tikrit, where 1,700 Iraqi soldiers were captured and then killed by IS militants.

National Bureau of Investigation spokesman Jari Raty said the court case will start in April. If guilty, the brothers face up to life imprisonment, which in Finland means being released — although not automatically — after serving between 12 and 15 years.

It was not known what the men had pleaded because their defense lawyers were barred from commenting.

The men had arrived in Finland in September but it was unclear whether they were asylum-seekers — although Finnish media claimed they are. Some 17,000 Iraqis have sought asylum in Finland so far this year, by far the biggest national group to seek shelter in the country.

The tabloid Ilta-Sanomat quoted Omar Mohammed, an asylum-seeker from Baghdad at the Forssa refugee center, as saying the brothers had avoided talking to other refugees.