The International Criminal Court's prosecutor has accused Boko Haram militants of committing crimes against humanity in Nigeria, mainly murder and persecution.

The office of prosecutor Fatou Bensouda says there is a “reasonable basis” to believe Boko Haram has launched a “widespread and systematic attack” that resulted in the deaths of more than 1,200 Christians and Muslims since mid-2009.

The report, which was leaked to media outlets, recommends that Nigerian authorities prosecute those crimes, or the ICC could do it itself.

Regarding accusations that Nigerian security agencies also committed human rights violations, the report said there is no indication that those alleged acts were part of a “state or organizational policy to attack the civilian population.”

Last month, Human Rights Watch said the conflict between Boko Haram and the Nigerian government has claimed more than 2,800 lives since 2009, with some 1,300 the result of action by Nigerian security forces.

The group said the violence escalated this year, with more than 815 killings in the first nine months alone.

Boko Haram says it is fighting to establish an Islamic state in northern Nigeria.