A 15-year-old Rohingya girl told HRW that soldiers stripped her naked and dragged her from her home to a nearby tree where about 10 men raped her.
"They left me where I was. When my brother and sister came to get me, I was lying there on the ground, they thought I was dead," said the girl from Hathi Para village in Maungdaw district.
She was one of the 52 female refugees that the New York-based rights body interviewed for the report that was published on Thursday.
Myanmar's army had earlier released a report denying all allegations of rape and killings by security forces which was termed "absurd" by a human rights group.
More than 600,000 majority-Muslim Rohingya have been forced to seek shelter in neighbouring Bangladesh and their homes and properties have been destroyed in arson attacks since August 25. Hundreds of them have also been killed by Myanmar soldiers and Buddhist mobs.
The report also quoted many rape survivors reporting "days of agony walking with swollen and torn genitals while fleeing to Bangladesh".
Sexual violence perpetrated by armyPramila Patten, the UN special envoy on sexual violence in conflict, said sexual violence was "being commanded, orchestrated and perpetrated by the Armed Forces of Myanmar".
Survivors and witnesses also told Al Jazeera accounts of women and girls being raped then locked inside houses that were torched.
They have recounted stories of torture, mutilations, being stripped naked and other atrocities and acts of humiliation.
"Rape has been a prominent and devastating feature of the Burmese military's campaign of ethnic cleansing against the Rohingya," said Skye Wheeler, women's rights emergencies researcher at Human Rights Watch and author of the report.
"The Burmese military's barbaric acts of violence have left countless women and girls brutally harmed and traumatised."
A statement by the UN migration agency IOM said its doctors had treated dozens of women who experienced "violent sexual assault" since August but said such numbers likely represent only a "small portion" of actual cases.
Such "egregious violence and abuse is underreported" even in a more stable situation, the agency said.
'Ongoing genocide'The HRW report said soldiers raped women and girls both during major attacks on villages and in the weeks prior to the attacks, after repeatedly harassing the Rohingya women and children.
|More than 600,000 Rohingya have been forced to seek shelter in neighbouring Bangladesh since August 25 [Anadolu]|
Two sisters who spoke to Al Jazeera said they were raped by Myanmar soldiers.
"The military tortured us," said 25-year-old Minara, who gave only one name. "They murdered our parents. They took us to the jungle. They pushed us down on the ground."
Her sister Aziza, 22, said she was raped by two men and became unconscious.
The two sisters were rescued by other refugees who helped them cross a river into Bangladesh.
HRW has requested the UN to "impose bilateral arms embargoes on Burma, and create and implement sanctions regimes - including travel bans, asset freezes, and restrictions on access to financial institutions".
Activists have said the international community needs to do more to stop Myanmar military from orchestrating "genocide" against Rohingya - one of the most persecuted communities in the world.
Watch :The Rohingya Exodus101 East Video