The source, speaking to AFP on condition of anonymity, said Hassan Saeed died along with two comrades as their car was hit on the road to Sinjar, the heartland of Iraq's Yazidi religious minority.

Saeed headed the Sinjar Resistance Units, set up in 2014 to protect the Yazidis from the Islamic State (IS) group before being integrated into the mainly pro-Iranian Hashed.

His force is seen as close to the Kurdistan Workers' Party (PKK), a group outlawed in Turkey that has rear bases in northern Iraq.

The PKK has since 1984 waged a rebellion in mainly Kurdish southeast Turkey that has claimed more than 40,000 lives.

Turkish forces routinely conduct operations against PKK bases in the rugged mountains of northern Iraq.

In its latest losses, Ankara said Monday that four Turkish soldiers were killed in two separate incidents in northern Iraq over the weekend.

Before they were targeted by IS, around 550,000 Yazidis had been living in Iraq's rugged northwest, concentrated around Sinjar.

But in 2014, the jihadists swept through Sinjar and, branding the Yazidis as infidels, killed the men, took boys as child soldiers and forced women into sexual slavery.

Several thousand Yazidis were killed and nearly 100,000 fled abroad. Some 360,000 remain displaced in the autonomous Kurdistan region of northern Iraq.