The United Nations Security Council on Thursday unanimously approved the establishment of a UN investigative team to help Iraq secure evidence of acts committed by the Islamic State group "that may amount to war crimes, crimes against humanity and genocide."

Britain, which drafted the resolution and has already promised to give 1 million pounds ($1.35 million, €1.14 million) to the investigative effort, said the team would bring some justice to those who had experienced IS atrocities in Iraq.

"There can never be adequate recompense" for those who have had to endure the group's brutality, British Minister of State for the Middle East Alistair Burt said. "This resolution means that the international community is united in our belief that there should at least be accountability for those who perpetrated such wanton acts."

Read more: 'Islamic State': Will it survive a post-caliphate future?

The US ambassador to the UN, Nikki Haley, called the resolution "a landmark" that would "provide an indispensable record of the scope and scale" of IS atrocities."

The vote, which took place in New York during the UN General Assembly, kicked off a 60-day window for UN Secretary-General Antonio Guterres to present details of the investigative team's mandate to the Security Council.

Months of pressure

Britain took up the initiative after Iraqi Foreign Minister Ibrahim al-Jaafari sent a letter to the Security Council in August requesting international help.

"The crimes committed by the terrorist organization ISIL against civilians and its destruction of infrastructure and antiquities in Iraq are crimes against humanity," al-Jaafari wrote using another acronym for IS.

Prominent international human rights lawyer Amal Clooney supported the resolution after months of calling on the Iraqi government to cooperate with UN investigators. Clooney represents women of Iraq's Yazidi minority who were kidnapped and held as sex slaves by IS militants after the terrorist organization conquered large swathes of Iraq in mid-2014.

Last year, the UN said IS was seeking to wipe out the religious minority in Iraq and Syria through actions is said amounted to genocide. Yazidi women, in particular, had suffered terrible abuse in captivity, investigators said.

Read more: From the Sinjar mountains to Germany's Rhineland: a Yazidi refugee's story

IS strongholds in Iraq and Syria collapsing

The establishment of the UN investigative team comes follows the Iraqi army's capture of Mosul, Islamic State's former stronghold capital in Iraq, in June after a 9-month campaign to retake the city that Iraqi security forces had lost in 2014.

The army started two separate offenses this week to retake the IS's last enclaves in Hawija, in the north, and the Euphrates Valley, in the west.

Across the border in Syria, US-backed rebels and government forces loyal to Syrian President Bashar al-Assad launched two separate offensives this week against IS's stronghold in Deir Ezzor near the Iraqi-Syrian border.

On Thursday, the Syrian Observatory for Human Rights, a war monitor, said IS had lost 90 percent of Raqqa, its de facto capital in the country, to rebel forces.

amp/sms (AP, AFP, Reuters, dpa)