A new report by the UN describes the "outrageous practices" used by gangs in Haiti to brutalise, punish and control the civilian population.
It says that the gangs, which are estimated to control more than 80% of the capital, Port-au-Prince, recruit and abuse children, sometimes killing those who try to escape.
UN Human Rights chief Volker Türk chief said the situation was "cataclysmic".
He warned that weapons continue to pour into the country.
The report published on Thursday found that there had been a significant increase in armed violence caused by criminal gangs in the five months leading up to March.
Gangs used sexual violence in particular to spread fear in areas where they fought for control, it says: "During gang attacks, several women and girls have been subjected to rape, including collective rape, in their homes, often after having witnessed the killing of their husbands."
It adds that some of the rape victims had been mutilated or killed after the attacks.
According to the report, Haiti's armed criminal gangs also inflicted violence on children.
The victim in one particular incident was a three-month-old baby while in a surge of violence in an area of the capital previously considered relatively safe, entire families were burned alive in their homes.