LAGOS, Nigeria (AP) -- Gunmen have killed at least 15 people in Nigeria's northwest, the Sokoto state governor said, the latest incident in a spiral of violence in Africa's most populous country.
The gunmen stormed communities in Sokoto state and raided houses from Sunday night into Monday morning, Gov. Aminu Tambuwal said in a statement, just days after nearly 30 people were shot dead across remote communities across Nigeria's troubled north.
At least 13 people were killed in Illela, a town near the border with neighboring Niger and some 97 kilometers (60 miles) from the state capital, he said, adding that two others were killed in Goronyo, about 76 kilometers (47 miles) east of the state capital.
The violent attacks across the northwest and central parts of Nigeria have killed hundreds of people this year.
Most affected communities are in remote areas that don't have adequate security or telecommunications, such as Goronyo community where more than 40 people were shot dead a month ago when assailants opened fire at a crowded marketplace.
The gunmen are mostly young men from the Fulani ethnic group who had traditionally worked as nomadic cattle herders and are caught up in a decades-long conflict with Hausa farming communities over access to water and grazing land, according to authorities and security analysts.
The attacks have taken on ethnic and religious dimensions, with clashes often reported in volatile states between the herdsmen and local communities. The assailants -- called bandits in Nigeria -- are "graduating into terrorists," Gov. Tambuwal said.
The widespread banditry in the northwest is in addition to the Islamic extremist insurgency in the northeast that has lasted more than a decade. Some of the bandits -- who often operate in bands of more than 100 -- are now joining forces with the extremist rebels, security analysts and residents have told AP.