BAGHDAD — When Islamic State militants retreated from the embattled town of Jurf al-Sakher last week, the Iraqi military was quick to flaunt a rare victory against the extremist group, with state television showing tanks and Humvees parading through the town and soldiers touring government buildings that had been occupied by the militants since August.

However, photos soon emerged on independent Iraqi news websites revealing a more discrete presence — the powerful Iranian general Ghasem Soleimani — whose name has become synonymous with the handful of victories attributed to Iraqi ground forces. Local commanders said Lebanon’s powerful Shiite Hezbollah group was also on the front lines.

Shiite militias have played a key role in driving the Islamic State group out of the so-called Baghdad Belt of Sunni villages ringing the capital. But the sectarian militias have long been implicated in brutality against the country’s Sunnis, and while they have benefited from U.S.-led airstrikes, their advance could undermine efforts to knit the troubled country together.

Militia commanders told The Associated Press that dozens of advisers from the Iranian Revolutionary Guard and the Lebanese Hezbollah were on the front lines in Jurf al-Sakher, providing weapons training to some 7,000 troops and militia fighters, and coordinating with military commanders ahead of the operation.