BAGHDAD — Two powerful Shiite militias are top suspects in the abduction of three Americans last weekend in a southern neighborhood of the Iraqi capital, an Iraqi police commander and a Western security official in Baghdad said today.

The Americans were abducted in Dora, a mixed neighborhood that is home to both Shiites and Sunnis, on Saturday. It was the latest in a series of brazen high-profile kidnappings undermining confidence in the Iraqi government’s ability to control state-sanctioned Shiite militias that have grown in strength as Iraqi security forces battle the Islamic State group.

Two Shiite militias  —Asaib Ahl al-Haq and Saraya al-Salam — were likely behind the attack, the Iraqi and Western official told The Associated Press today.

“Nobody can do anything in that neighborhood without the approval of those militias,” the police commander said. The Western security official confirmed that Iraqi and U.S. intelligence assessments had narrowed down the suspects to those the two groups.

Both officials spoke on condition of anonymity because they were not authorized to talk to reporters.