A UN investigation into China's treatment of Muslim minorities in its vast Xinjiang region has reported torture, sexual abuse and possible crimes against humanity, but stopped short of describing it as genocide.

The report was immediately met by a lengthy rebuttal from China's mission to Geneva.

Here are five main allegations from the UN and China's responses:

Mass arbitrary detention

The UN report describes a "pattern of large-scale arbitrary detention" in Xinjiang, in which individuals suspected of terrorism are held in high-security facilities without due process and for indefinite lengths of time.

Everything from having too many children, wearing a veil or beard, or not using one's passport are cited as behaviors that can lead authorities to identify individuals as being at risk of "extremism" and mark them for possible detention.

More recently there have been signs of a shift toward formal jail terms "as the principal means for large-scale imprisonment and deprivation of liberty", according to the report.

Many have been detained without their family members being informed, it also notes.

China has dismissed allegations of mass arbitrary detention as "lies". It insists it has "clearly specified" definitions of terrorism and extremism that have "ruled out arbitrary enforcement due to vague, over-stretching and general legal provisions".

Torture

The report says it found "credible" allegations of torture and sexual assault — including rape — at detention centers in Xinjiang.

Former detainees interviewed by the UN describe being beaten while immobilized in "tiger chairs" — used by Chinese police to restrain interrogation subjects — and being forced to receive unexplained medical treatments, as well as instances of rape and "invasive gynaecological examinations".

"The Government's blanket denials of all allegations, as well as its gendered and humiliating attacks on those who have come forward to share their experiences… have added to the indignity and suffering of survivors," the UN report says.

China insists the centers "fully guarantee that trainees' personal dignity is inviolable, and prohibit any insult or abuse of them in any manner".

Beijing has publicly condemned women who made claims of sexual assault in the camps, using their alleged sexual health and relationship statuses in an attempt to discredit them.

Forced sterilizations and abortions

The UN says it spoke to women who recounted being "forced to have abortions or forced to have IUDs inserted" — claims it said were believed to be credible. 

Noting a sharp decline in Xinjiang's birth rates from 2017, as well as a Beijing white paper linking frequent births and religious extremism, the UN's human rights office says "there are credible indications of violations of reproductive rights through the coercive enforcement of family planning policies".

China dismisses claims of forced sterilizations as "disinformation", saying people in Xinjiang are voluntarily opting to marry later and have fewer children due to improved education and living conditions.

Suppression of religious freedom