YANGON, Myanmar (AP) — A human rights group urged Myanmar's government on Monday to back an independent international investigation into alleged abuses by security forces against members of the Muslim Rohingya ethnic minority, including the reported systematic use of sexual violence.

U.S.-based Human Rights Watch said in a statement that soldiers and Border Guard Police took part in rape, gang rape, invasive body searches and sexual assaults while conducting counter-insurgency operations in the western state of Rakhine from October through mid-December.

The estimated 1 million Rohingya face official and social discrimination in Buddhist-majority Myanmar, also known as Burma. Most do not have citizenship and are regarded as illegal immigrants from Bangladesh, even when their families have lived in Myanmar for generations. Communal violence in 2012 forced many to flee their homes, and more than 100,000 still live in squalid refugee camps.

"The sexual violence did not appear to be random or opportunistic, but part of a coordinated and systematic attack against Rohingya, in part because of their ethnicity and religion," Human Rights Watch said.

"These horrific attacks on Rohingya women and girls by security forces add a new and brutal chapter to the Burmese military's long and sickening history of sexual violence against women," said Priyanka Motaparthy, the group's senior emergencies researcher. "Military and police commanders should be held responsible for these crimes if they did not do everything in their power to stop them or punish those involved."

Myanmar's military has long been accused of human rights abuses against members of the country's other ethnic minorities, often while conducting counterinsurgency operations.

The United Nations High Commissioner for Human Rights made similar allegations in a detailed report released Friday. Other human rights groups have also criticized the treatment of Rohingya civilians.

The U.S. State Department said Monday it was "deeply troubled" by the findings of that report, and urged the Myanmar government to take its findings seriously, but stopped short of endorsing the idea of international investigation.

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France's Foreign Ministry took a stronger stand. It said the reported rights violations were "unacceptable" and noted that the report would be examined by the U.N. Human Rights Council.

The U.N. agency report, based on interviews with more than 200 Rohingya who fled to neighboring Bangladesh, said the violence against the Rohingya has been widespread and seemingly systematic, involving killings, enforced disappearances, torture, rape and other sexual violence, arbitrary detention and deportation, "indicating the very likely commission of crimes against humanity."

It said of the 101 women interviewed, "more than half reported having suffered rape or other forms of sexual violence."

Human Rights Watch said Myanmar authorities "have taken no evident steps to seriously investigate allegations of sexual violence or other abuses reported by non-governmental organizations" and has tried instead to discredit them.

"The government should stop contesting these rape allegations and instead provide survivors with access to necessary support, health care, and other services," Motaparthy said.

A spokesman for the Myanmar president's office could not be reached for comment. The government has consistently denied abuses and has blocked independent journalists and aid workers from visiting the military's operation zone in northern Rakhine.

The government launched what it called "area clearance operations" in northern Rakhine after attacks on border police killed nine officers. It blamed a little-known Muslim insurgent group for the attacks.

Friday's U.N. human rights report said the military operations launched in October "have likely resulted in several hundred deaths and have led to an estimated 66,000 people fleeing into Bangladesh and 22,000 being internally displaced."