Amnesty International says rebel groups who took control of northern Mali following a coup are committing serious human rights abuses, including sexual violence, murder and use of children as combatants.

The British-based human rights group said Wednesday that Malian soldiers have also carried out arbitrary detentions and extra-judicial executions in the conflict, calling it Mali's worst crisis in 50 years.

The rights group, which recently conducted a three-week research mission to Mali, spoke with young girls who reported being gang-raped by separatist Tuareg rebels.

It also said there is evidence that an armed Islamist group in the region is using child soldiers and forcing citizens to comply with its radical interpretation of Islamic law.

The armed groups took control of northern Mali following a March coup by renegade soldiers who accused the government of failing to properly equip the army to handle the rebellion.

Since then, Mali's interim government has been unable to focus on the crisis in the north, which has displaced tens of thousands of people.