A UN team authorised over a year ago to investigate the massacre of the Yazidi minority and other atrocities by jihadists in Iraq will finally begin work early next year, the head of the investigation said Tuesday.

The UN Security Council adopted a resolution in September 2017 to bring those responsible for Islamic State group war crimes to justice -- a cause championed by Nobel Peace Prize winner Nadia Murad and international human rights lawyer Amal Clooney.

The team, led by British lawyer Karim Asad Ahmad Khan, was deployed to Baghdad in October, but has since focused on administrative and technical details to lay the groundwork for the probe.

"The investigative team now looks forward to continuing preparations in Iraq with a view to commencing investigative activities in early 2019," Ahmad Khan told the council during his first report.

The Iraqi government had resisted calls for the UN probe and the head of the investigative team stressed that much effort had been deployed to ensure cooperation from Baghdad.

Ahmad Khan told the council that "the realization of our investigative activities is dependent on securing the cooperation, support and trust of all elements of Iraqi society."

The United Nations has described the massacre of the Yazidis by IS jihadists as possible genocide and UN rights investigators have documented horrific accounts of abuse suffered by women and girls.

Nadia Murad is among thousands of Yazidi women who were taken hostage and held as sex slaves when IS fighters swept into Iraq's Sinjar region in August 2014.

The investigators will gather evidence on war crimes, crimes against humanity or genocide for use in Iraqi courts that will hold trials for IS militants, according to the UN resolution.

More than 200 mass graves containing up to 12,000 bodies have been recently discovered in Iraq, providing evidence of war crimes by IS.

The United States announced it will provide $2 million to support the work of the investigative team, known as UNITAD, the UN investigative team to promote accountability for crimes committed by Daesh, an Arabic acronym for IS.

After being awarded this year's Nobel Peace Prize, Murad said she wanted IS jihadists to face trial in a courtroom.

"For me, justice doesn't mean killing all of the Daesh members who committed these crimes against us," she said in October.

"Justice for me is taking Daesh members to a court of law and seeing them in court admitting to the crimes they committed against Yazidis and being punished for those crimes specifically," she said in October.