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 Thursday.

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, which 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 on Thursday.

“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.

One of the militias named as a suspect is backed by Iran, a key ally of Iraqi Prime Minister Hayder al-Abadi’s government.

Al-Abadi said on Thursday that he doubts that there is an Iranian link to the kidnapping, adding “we don’t know if they have been kidnapped… they just went missing.”

The U.S. Embassy in Baghdad has confirmed that several Americans are missing and said they are working with Iraqi authorities to locate them.

Baghdad authorities said the three Americans were kidnapped from a “suspicious apartment” without elaborating, and have provided no other details. There has been no claim of responsibility.