When their mother asked a soldier at a nearby checkpoint what had happened to them, she said the soldier replied, “We do not know where they took them, and we could not ask because they are more powerful than us.’ ”

That language alone is enough to leave most Sunnis with a sense of foreboding and a memory of the days when militias were above the law.

A worrisomely growing number of these abducted men show up at the Baghdad morgue. In the third week of June, at least 21 unidentified bodies, most shot in the head, were found in Baghdad, a United Nations official said. Police officials found 23, said an Interior Ministry official, speaking on the condition of anonymity as a matter of policy. Others simply disappear, most likely into the overcrowded Iraqi prisons, but no one knows for sure.

“We certainly acknowledge there are unidentified bodies being found in Baghdad, and some evidence is emerging that people have been tortured,” said Jacqueline Badcock, the deputy representative of the secretary general for Humanitarian and Development Affairs for the United Nations office in Iraq.

“The numbers are relatively small, but they’re rising,” she said. “It’s alarming.”

Day in and day out, Baghdad’s Sunnis are closely watched in crowded neighborhoods. Suspicions that they are secretly siding with the Sunni insurgents only grow as the militants get ever closer to Baghdad, they say, and increase their fears of retaliation.

Baghdad Sunnis in six neighborhoods said in interviews that they had been treated more harshly since ISIS took over Mosul on June 10. While there have been abductions and killings of Sunnis for months, after Mosul they began to sense that they were being targeted because of their sect.