LONDON — The police in Finland arrested Iraqi twin brothers on Tuesday suspected of being members of the Islamic State and of shooting 11 unarmed prisoners in Iraq in June 2014, Finnish news reports said yesterday (Dec 10).

Finland’s National Bureau of Investigation said yesterday that the men had arrived in Finland in September and were arrested following an investigation. News reports said they did not resist arrest.

Finnish law enforcement officials did not specify whether the men had arrived as part of the influx of migrants to Europe from the Middle East and beyond. But the Finnish national broadcaster, Yle, reported that the men, age 23, were asylum seekers, and the arrests intensified concerns that terrorists were slipping into the stream of refugees in an effort to avoid detection by security forces.

Fears that Islamic radicals might be entering Europe posing as migrants were fanned in the aftermath of the terrorist attacks in Paris last month when the police discovered a Syrian passport near the body of one of the suicide bombers. The authorities said that the same passport or a copy of it had been used by a refugee to register on the Greek island of Leros in October, and then in Serbia and Croatia.

Like a number of other European countries, Finland has been taking steps to make the country a less attractive destination for migrants, who have long sought to reach the northern European nations with reputations for the most generous social welfare systems and most welcoming societies. The sheer scale of the refugee flow * roughly 1 million migrants have reached Germany alone this year * has overwhelmed Europe, and has led nations along the main migrant trail to restrict access to all but those coming from the most war-torn nations: Syria, Iraq and Afghanistan.

Mikko Majander, adjunct professor of political history at the University of Helsinki, said the arrests announced yesterday threatened to fan a simmering anti-immigrant backlash in Finland and Europe as a whole. “This is the big question, whether they were smuggled in as asylum seekers, and it is fueling alarm at a time when there are already concerns about migration and who is coming here,” he said.

He said an estimated 32,000 refugees had entered Finland so far this year, many from Iraq and Afghanistan, and that the migrant crisis was stoking some resentment in a country that does not have a strong history of immigration.

Yle, citing the National Bureau of Investigation’s chief inspector, Jari Raty, said the men were suspected of killing 11 people during a massacre by the Islamic State of as many as 1,700 unarmed Iraqi soldiers in June 2014 at Camp Speicher near Tikrit, northwest of Baghdad.

The broadcaster said the soldiers had been taken prisoner after an attack on a bus and that the Islamic State had made a propaganda video of the killings. “The victims were lying on the ground and they were shot one by one,” Raty was quoted as saying by the broadcaster. He said that the gunmen were not wearing masks at the time, and law enforcement officials said that proved crucial to identifying them. THE NEW YORK TIMES