ISIL's genocide against Iraq's Yazidis is still "ongoing" and remains "unaddressed" by the international community, the UN has said, marking three years since ISIL began killing and capturing thousands of members of the religious minority group.

The UN human rights Commission of Inquiry, which declared the killings of thousands of Yazidis by ISIL, or the Islamic State of Iraq and the Levant group, to be a genocide, said on Thursday that the atrocity had not ended and that the international community was not doing enough to stop it.

"The genocide is ongoing and remains largely unaddressed, despite the obligation of states ... to prevent and to punish the crime," the commissioners said in a statement.

Fighters were driven out of the last part of the Yazidi homeland in northern Iraq in May.

However, most Yazidis have yet to return to villages they fled when the group overran Sinjar in the summer of 2014, killing and capturing thousands because of their faith.

Nearly 3,000 Yazidi women and children remain in ISIL captivity, and control over Sinjar is disputed by rival armed groups and their regional patrons.

Justice for the crimes Yazidis suffered, including sexual enslavement, has also so far proved elusive.

"The Yazidis' wound is still bleeding," one man told Reuters news agency at a ceremony attended by several thousand people including the mayor and other local dignitaries, held at a temple at the foot of the mountain that dominates Sinjar.

"The Kurds and the Iraqi government are fighting for Sinjar and we are paying the price," the man said.

ISIL kidnapped Yazidis from Sinjar and forced them to become sex slaves or fighters [Rodi Said/Reuters]

ISIL fighters killed thousands of captured men during their attack on the Yazidis, a religious group whose beliefs combine elements of several ancient Middle Eastern religions and is abhorred by ISIL.

About 3,100 Yazidis were killed - with more than half shot, beheaded or burned alive - and about 6,800 kidnapped to become sex slaves or fighters, according to a report published in the Public Library of Science journal PLoS Medicine.

Enslaved women and girls are now reportedly being sold by ISIL fighters trying to escape the US-led coalition's assault on the group's Syrian stronghold of Raqqa, the UN commission said.

Control over Sinjar

The array of forces that drove ISIL, also known as ISIS, out of Sinjar are now vying for control of the area near the borders of Iraq, Syria and Turkey.

Kurdish Peshmerga forces retook around half of Sinjar in late 2015, effectively annexing it to the autonomous region they hope to convert into an independent state.

A referendum on independence is due to be held in September, which the government in Baghdad opposes.

Mainly Shia groups, some backed by Iran, retook the rest of the Yazidi homeland in May, bringing them within metres of the Peshmerga forces.

Another group, Kurdistan Workers Party (PKK), which is outlawed in Turkey, also gained a foothold in Sinjar and clashed with the Peshmerga earlier this year.

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The PKK's presence has made the area a target for Turkey.

"People are worried about returning," General Ashti Kojer, the local head of Kurdish police, said.

"The [Sinjar] region has become a conflict zone."

Kojer and another local official said the political environment was preventing international organisations from working on reconstruction and rehabilitation in Sinjar, further discouraging Yazidis from returning.

'Stop Yazidi Genocide'

In a speech at Thursday's ceremony, Mahma Xelil, the Yazidi mayor of Sinjar, said Nuri al-Maliki, the former Iraqi prime minister, was responsible for the tragedy because he was in charge when the ISIL fighters overran Mosul.

Other Yazidis blame the Kurds, who were defending the area at the time, for failing to resist the ISIL onslaught.

At the ceremony, people carried signs saying "Stop Yazidi Genocide". Families streamed into cemeteries to remember their loved ones. Women wore bandanas saying "Genocide".

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In the city of Sinjar, posters and banners hung up on roundabouts depict harrowing scenes from the attack three years ago: families fleeing and distressed women and children.

Large parts of the city, which was also home to Muslim Kurds and Arabs, remain empty.

Around 1,000 Yazidi families have returned to Sinjar since the city was retaken in 2015, according to Jalal Khalaf, the director of the mayor's office in Sinjar.

The city and the surrounding area had been home to around 400,000 Yazidis.

Source: Reuters news agency