Gunmen shot or hacked to death about 10 people during a raid on two neighbouring villages in Nigeria's remote northwestern state of Zamfara, police said on Sunday, in an area plagued by Islamist militancy and lawlessness.
The motive for the attack late on Saturday on the villages of Makera and Usu was not known, police said. It was also unclear whether militant Islamist sect Boko Haram or a criminal gang were behind it.
"There was an attack in these villages in Zamfara and people were killed. I think the number is around 10," Zamfara police spokesman Hassan Usman Talba said by telephone from the scene. He said the prime suspects were gangs of Fulani herdsman but that police were still investigating.
The Fulani's semi-nomadic, cattle-herding way of life has led to decades of conflict with farming communities across central and northern Nigeria that often erupts into violence.
The focus of Nigeria's Islamist insurgency has been northeastern Borno state and surrounding areas, but a military crackdown this year has pushed it into several states further south and west, including Zamfara.
Analysts say the insurgency has also brought a breakdown of law and order across the north, creating opportunities for armed gangs and ethnic militias with scores to settle.
Islamist militancy and associated insecurity are the biggest threats to stability in Africa's main oil exporter.
Boko Haram, which is loosely based on the Afghan Taliban, killed hundreds last year in a campaign to impose sharia, or Islamic law. Nigeria's more than 160 million people are split roughly equally between Christians and Muslims.