Gunmen have killed at least 20 people in an attack in a gold mining village in Nigeria’s northwestern Zamfara state, residents and Amnesty International said, Reuters reported

Details on a possible motive for the attack were not immediately known but Zamfara state has grappled with kidnappings for ransom by armed gangs, who also target security forces.

Ismail Hassan, a resident, told Reuters that gunmen in their hundreds opened fire on miners on Thursday afternoon and a firefight ensued with over 20 people dead in the mining village of Gobirawa Chali in the Maru local government area of Zamfara state.

Another resident, Isah Ibrahim, said they had recovered 21 bodies following the attack and that several were injured.

Amnesty International said in a statement the gunmen went house-to-house in Gobirawa Chali, killing over 20 people, according to Reuters.