At least 1,200 people have been killed in the last four years in northern Nigeria by the militant Islamist group Boko Haram, according to a preliminary investigation by the International Criminal Court, World Watch Monitor reports. The Court's chief prosecutor, Fatou Bensouda, said on Monday the ICC is investigating Boko Haram for "crimes against humanity" through "widespread and systematic attacks," the scale and intensity of which have increased over time. The initial ICC report is based on statistics leading up to December 2012. The ICC is now considering whether it merits further investigation. The International Criminal Court, based in The Hague, tries cases of crimes against humanity, war crimes and genocide when a country's own courts fail to prosecute. Nigeria agreed in 2001 to subject itself to the jurisdiction of the ICC. Pastor Ayo Oritsejafor, president of the Christian Association of Nigeria, agreed that the rate of attacks is intensifying. In a recent speech, he said: "In my first term, about 3000 Christians were killed. Last year alone averaged over 100 every month. In March 2010, about 500 Christians were slaughtered in one night on an attack on their villages. In April 2011, our members lost over 500 churches, thousands of homes and businesses in a 48 hour period and in 2012 about 70 percent of all Christians killed worldwide were in northern Nigeria alone."