A Kurdish Peshmerga commander has accused a Baghdad-sponsored umbrella organization of mostly Iran-allied Shiite militias of arresting three of their fighters in northern Iraq’s predominantly Sunni Nineveh province amid flaring tensions between the two groups.

The incident took place in Bashiqa, a town in northeast of Mosul, recently liberated from the Islamic State (ISIS/ISIL).

U.S.-backed Iraqi forces and members of the Iran-allied Popular Mobilization Units (PMU), also known as the Popular Mobilization Forces (PMF) and Hashd al-Shaabi, have pushed the jihadist group out of Mosul, the capital of Nineveh.

“The presence of the PMF in areas liberated from ISIS [like Mosul] would likely increase ethnic tensions with the Kurds and Sunni Arabs and may lead to violent clashes,” warned the Defense Intelligence Agency (DIA) in its most recent World Threat Assessment.

PMU troops have already clashed with Kurdish Peshmerga fighters on several occasions in northern Iraqi towns primarily inhabited by Yazidis, namely Sinjar and now Bashiqa. The Kurdish Peshmerga cleared ISIS out of both places.

Sinjar also sits in Nineveh province, right outside of the autonomous Iraqi Kurdistan Region that borders Shiite powerhouse Iran.

“Hashd al-Shaabi forces who are 300 to 400 meters away from us arrested three Peshmerga fighters after they entered an old ISIS tunnel,” Iraqi Kurdish Maj. Gen. Halgord Khidir told Rudaw.

“The three Peshmerga are currently held by the Hashd al-Shaabi forces who have decided to release them tomorrow,” he added.

Most of the Kurds in Iraq are Sunni.

Some Yazidis have accused the Kurds of stealing their lands. Vowing to put the Yazidis back in control of Sinjar, the PMU has managed to recruit some members of the minority group, which has been devastated by ISIS.

A PMU-affiliated group bombed Kurdish Peshmerga positions in Sinjar, also spelled Shingal, back in January.

That month, Iraqi Kurdish leaders expressed disdain towards the presence of the PMU in Iraqi Kurdistan, accusing them of trying to establish a base in the region and recruiting Kurds into their ranks.

“They have come closer to here [Iraqi Kurdistan] in order to recruit Kurds and we should all stop that,” declared Sheikh Jaafar Mustafa, a top Kurdistan Democratic Party (KDP) official, referring to the PMU.

“This will lead to trouble in the area and a limit should be put on these kinds of Hashd activities,” he added.

The autonomous Kurdistan Regional Government (KRG) is expected to move forward with a referendum on independence this year despite opposition from Baghdad.

Amid the Mosul offensive in November 2016, the Iraqi parliament enacted a law that legalized the PMU.

The DIA reported:

Iraqi security forces’ shortcomings are likely to prompt a continued security role for the Popular Mobilization Forces (PMF), the umbrella for a diverse array of militias largely dominated by Iranian-aligned Shia militia groups, which have gained popularity and political influence with some officials and probably much of the Shia populace in Iraq as a result of their successes in most counter-ISIS battles in 2016.

Although the PMU is mostly Shiite, its members also include Sunni tribesmen, Kurds, Yazidis, and Christians.