Armed gangs killed 57 people in a string of attacks on villages in northwest Nigeria, residents said on Wednesday, as security forces struggle to curb violence in the region.

Roughly 150 gunmen on motorcycles opened fire on residents before looting shops and stealing cattle in a series of assaults on Tuesday in six remote communities in Katsina state, the sources said.

“We lost a total of 57 people in the attacks across the six villages,” a local leader told AFP on condition of anonymity as he feared for his safety.

In the worst-hit village of Kadisau the assailants — dubbed “bandits” by locals — shot and killed 33 people, local resident Mohammed Salisu said.

Salisu said he escaped by abandoning his motorcycle and hiding in a ditch before crawling into a nearby house where he hid among dirty laundry for the five hours the attack and looting lasted.

“They looted every shop in the village and took away over 200 cattle,” said Salisu, who lost seven cows to the attackers.

The attackers opened fire on a football pitch where young men were watching a local match, said Sada Audi, a resident of nearby village said.

Residents said 24 more people were later killed across the villages of Hayin Kabalawa, Garke, Makera, Kwakwere and Maiganguna.

The assailants left two dozen people with bullet wounds, inhabitants said.

Nigeria’s northwest has been wracked by years of violence, involving clashes between rival communities over land, attacks by heavily armed criminal gangs and retaliation strikes from vigilante groups.

The unrest, which experts say has been spurred by overpopulation and climate change, has seen an estimated 8,000 people killed since 2011 and 200,000 flee their homes.

Nigeria’s military last month said it had launched air raids to halt a spike of attacks in President Muhammadu Buhari’s home state of Katsina.

Authorities have carried out several security operations and local peace negotiations in the region but have failed to end the bloodshed.