Five women who were part of the al-Khansa Brigade (also spelled al-Khanssaa Brigade), an all-women police of the Islamic State (Isis) terror group, were gunned down by unknown vigilantes in the Iraqi city of Mosul, BasNews reported.

The women were killed during an attack on the base of the al-Khansa Brigade by an armed group - claimed to be local vigilantes opposed to the Islamic State. A Kurdistan Democratic Party official from Mosul told the local media that the attack was just one of the several carried out by anonymous armed groups against Isis in its stronghold.

The al-Khanssa Brigade works as an ultra-conservative religious enforcement unit that monitors the behaviour of women inside Isis-held cities. The Isis female police also is tasked with the duties of maintaining the Isis brothels, where women are kept as sex slaves by the Sunni terror group.

Several British women have been found to be part of the dreaded religious police unit. It has been reported that the unit is headed by Aqsa Mahmood, a 20-year-old woman from Glasgow.

Mosul, which is the second largest city in Iraq, has been under the control of the Islamic State militants since June 2014.

[Also Read] Iraq: Shadowy Resistance Group Attacks 'Highly Professional' Radio Station Run by Isis in Mosul

In recent months, armed resistance groups inside Mosul have targeted Isis on several occasions. Last week, two unidentified gunmen, part of an unknown resistance group in Mosul, attacked a radio station run by the Islamic State (Isis) militants.

In April, a shadowy Sunni vigilante group released a video showing armed militia hunting down Isis terrorists inside the Iraqi city. The Sunni resistance group from Mosul was trained by the Kurds and were carrying out covert sniper attacks against Isis fighters.

The video clip also showed members of the guerilla outfit kidnapping and executing an Isis fighter.