Mali is "descending into hell" because of the executions, rape and torture taking place in its north, said a report by the International Federation for Human Rights (FIDH) published in Paris Thursday.
The report, which uses evidence from local rights groups operating in Mali, lists dozens of murders and gang rapes by armed groups since January.
"This report presents the investigation and reports collected in northern Mali which show that dozens of systematic rapes, summary execution and lootings have been committed as armed groups have taken control of the north's big cities," said FIDH president Souhayr Belhassen.
Mali subsequently said it would ask the International Criminal Court (ICC) to investigate the "atrocities" taking place.
"Next week Mali will officially refer the atrocities committed in the north of Mali by different armed gorups to the ICC," said a spokesman for the justice ministry.
The FIDH also asked ICC to open a preliminary inquiry into the rights abuses and called on the international community to "intensify actions to reestablish legitimate authority in Bamako and speed up political transition."
Rebels belonging to the Tuareg National Movement for the Liberation of Azawad (MNLA) and members of the hardline Islamist group Ansar Dine (Defenders of Faith) are blamed for a number of incidents of rape, violence and murder outlined in the report.
The groups are accused of being behind an attack on January 24 on a Malian army camp where 153 soldiers were taken prisoner and then executed.
In another incident, after fighters took the town of Gao in March, the heads of certain troops were seen "hanging on the camp wall and over the Wabaria bridge", according to one eyewitness account.
The report also details "over 50 rapes or attempted rates", often by gangs and including on young girls.
"These crimes that took place after taking towns in the Timbuktu and Gao region by Tuareg rebel forces seem to have targeted black women" living in the region, says the report.
Both Tuareg rebels and Ansar Dine -- who have in recent days destroyed a number of ancient saints' tombs in the fabled city of Timbuktu -- are said to have enlisted child soldiers in their campaign to dominate Mali's north.
Ansar Dine is recruiting children aged 12-15 to fight with its rebels and taking them to its camps a few kilometres from Gao, says the report.
Local communities have also been subjected to violent punishments since the star of the year including whippings for unmarried couples and the chopping off of hands as Islamists seek to impose Sharia law.
Mali spiralled into crisis after Tuareg rebels launched a rebellion in the north of the country in January, quickly overwhelming a demoralised and poorly equipped Malian army.
A coup in Bamako only worsened the situation as the unmanned north became easy prey and fell to rebel groups in a matter of days.
Islamist fighters from Ansar Dine appeared alongside the MNLA rebels but later turned against them, backed by Al-Qaeda in the Islamic Maghreb (AQIM) and an Al-Qaeda offshoot, and have now routed them.