Sheikhan (Irak) (AFP)

Thousands of Yazidis who survived atrocities at the hands of the Islamic State group bid a last farewell in Iraq on Monday to their spiritual leader who died last month.

The longtime head of the world's Yazidi minority, Prince Tahseen Said Ali, died in the KRH Siloah hospital in Hanover, Germany at the age of 85 at the end of January.

Incense floated in the air as thousands of mourners, both men and women, solemnly lined the side of the road to the mountaintop temple in the holy town of Lalish watching his wooden coffin go by.

Musicians dressed in white played flutes and drums as they accompanied the funeral cortege on Monday, the eve of the prince's burial in the northern Iraqi town.

"It's a day of great sadness," said one of the mourners, Abdel Khamuma.

His death had left "an immense void", he told AFP.

The Yazidi people were brutally targeted by the IS jihadists who swept across northern Iraq in 2014 and seized their bastion of Sinjar near the border with Syria.

IS fighters slaughtered thousands of Yazidi men and boys, then abducted women and girls to be abused as "sex slaves".

According to authorities, more than 6,400 Yazidis were abducted and only half of them were able to flee or be rescued.

The fate of the others remains unknown.

The brutal assault pushed around 360,000 of the Kurdish-speaking Yazidis to flee to other parts of Iraq, including the Kurdish region, in addition to another 100,000 who left the country altogether.

The United Nations has said IS's actions could amount to genocide, and is investigating the jihadist group's atrocities across Iraq.

The Yazidi faith emerged in Iran more than 4,000 years ago and is rooted in Zoroastrianism, over time integrating elements of Islam and Christianity.

With no holy book and organised into castes, Yazidis pray to God facing the sun and worship his seven angels -- first and foremost Melek Taus, or Peacock Angel.

Of the world's 1.5 million Yazidis, around 550,000 were living in the remote corners of northern Iraq, where their holiest site Lalish lies and where Prince Tahseen was born, before the IS onslaught.

Prince Tahseen, whose body arrived in Iraq from Germany on Monday, will be buried in Lalish on Tuesday.

The Yazidi cause has found a powerful symbol in Nadia Murad, a former IS abductee from Sinjar who escaped and went on to win the Nobel Peace Prize for her activism against sexual violence.

Prince Tahseen was born in 1933 in Iraq's northwest Sheikhan district and was appointed head of the Yazidis at age 11 after the death of his father, who was the previous emir.

He later moved to Germany, home of the biggest expatriate Yazidi community.

Iraqi Yazidi parliamentarian Vian Dakhil has told AFP that before dying, Prince Tahseen had appointed his son, Hazem, to succeed him.