Government forces have used rape and other sexual violence against men, women and children during the Syrian uprising, Human Rights Watch said.
The US-based group said it had recorded 20 incidents from interviews inside and outside Syria with eight victims, including four women, and more than 25 other people with knowledge of sexual abuse - including medical workers, former detainees, army defectors, and women's rights activists.
"Sexual violence in detention is one of many horrific weapons in the Syrian government's torture arsenal and Syrian security forces regularly use it to humiliate and degrade detainees with complete impunity," said Sarah Leah Whitson, Middle East director at HRW.
"The assaults are not limited to detention facilities - government forces and pro-government shabiha militia members have also sexually assaulted women and girls during home raids and residential sweeps."
Cases were reported all around Syria, but most of all in Homs province, an epicentre of the revolt.
HRW quoted a man who said he had been held in the Political Security branch in Latakia in a cell with over 70 other people. He said young boys were treated worse than adults, brought back to the cell raped and with their fingernails pulled out.
"One boy came into the cell bleeding from behind. He couldn't walk. It was something they just did to the boys. We would cry for them," the man said.
HRW said many of the assaults were in circumstances in which commanding officers knew or should have known the crimes, such as electric shocks to genitalia, were taking place.
In another face-to-face interview a woman from the Karm al-Zeitoun neighbourhood of Homs city which was overrun by Assad's troops said she heard security forces and shabiha militia rape her neighbours while she hid in her apartment in March.
"I could hear one girl fighting with one of (the men)... She pushed him and he shot her in the head," HRW quoted the woman as saying. She said three girls, the youngest aged 12, were then raped. After the men left the woman went next door.
"The scene on the inside was unreal. The 12-year-old was lying on the ground, blood to her knees... More than one person had raped the 12-year-old... She was torn the length of a forefinger. I will never go back there. It comes to me. I see it in my dreams and I just cry."
Some interviewees told HRW that victims did not want their families to know about the assault because of fear or shame. In one case, HRW said a female rape victim was willing to be interviewed but her husband forbade it.
"Even when they may wish to seek help, Syrian survivors of sexual assault have limited access to medical or psychological treatment and other services," HRW said.
"It is critical that survivors of sexual assault have access to emergency medical services, legal assistance, and social support to address injuries caused by the assault; prevent pregnancy, HIV, and other sexually transmitted infections; and to collect evidence to support prosecution of perpetrators."