U.N. chief Ban Ki-moon has condemned recent attacks by Islamic militants that killed hundreds of people in Nigeria, which holds elections next month even though Boko Haram extremists hold large swaths of territory in the northeast of Africa's most populous country.

Ban's office said in a statement Sunday that the secretary-general was appalled by reports that hundreds of civilians were slaughtered in an assault around Baga town in Borno state, near Nigeria's border with Chad. Some reports say the death toll is as high as 2,000.

Additionally, Ban's office cites reports that extremists used a 10-year-old girl as a suicide bomber Saturday to kill 19 people at a market in Maiduguri, also in Borno state.