Syrian troops and regime-linked militia have systematically used rape and sexual violence against civilians, atrocities that amount to crimes against humanity, a UN-backed inquiry said Thursday.  The Independent International Commission of Inquiry for Syria (COI) notes in its report that regime troops detained "thousands of women and girls" from 2011 to the end of 2017, the period covered in the report.  "During interrogation, women and girls... were beaten with pipes while hanging from the ceiling and electrocuted on their breasts and vaginas," it said.  A woman from Syrias third city of Homs told COI investigators that in 2012 "government forces entered her home and raped her daughter in front of her and her husband before shooting the daughter and the father", the report said.  "The mother was then raped by two soldiers," it added, in one of many examples of extreme violence.   The findings, submitted to the United Nations Human Rights Council, are based on 454 interviews with sources that include survivors, eye witnesses and medical workers. While women have been the most frequent victims of rape, sexual violence against men and children -- girls and boys -- was also documented.  The COI found that "rapes and other acts of sexual violence carried out by government forces and associated militias during ground operations, house raids, at checkpoints, and during detention formed part of a widespread and systematic attack directed against a civilian population, and amount to crimes against humanity." In contrast, it found "no evidence of a systematic practice or policy on the part of armed (rebel) groups to use sexual and gender-based violence to instill fear, extract information, or enforce loyalty," even if the opposition members have repeatedly committed sexual violence.  That finding does not apply to ISIS, whose widespread atrocities including sexual violence have been separately documented by the COI.  Paulo Pinheiro is the chairman of the UN Commission of Inquiry. The independent experts - who have compiled confidential lists of suspects since 2011 - did not name individual perpetrators but said they had documented "numerous" cases of rapes by high-level officers.