Gunmen killed five worshippers and kidnapped at least 18 in an attack on a mosque in northwestern Nigeria’s Zamfara state, police said.

Speaking to AFP news agency on Sunday, state police spokesman Mohammed Shehu said: “The bandits killed five worshippers and kidnapped 18 others, including the imam.”

According to reports, about 100 cattle thieves on motorcycles opened fire on a Muslim congregation in remote Dutsen Gari village in Maru district as residents were observing weekly Friday prayers.

“The gunmen attacked the mosque while the imam was delivering the sermon and took away more than 30 people, including the imam, after shooting dead five worshippers,” one resident, Ibrahim Altine, said.

Northwest Nigeria is a hotbed of criminal gangs accused of raiding villages, stealing cattle, kidnapping for ransom and burning homes after looting food supplies.

The country’s northwest sees occasional clashes between the herder Fulani people, one of the largest ethnic groups widely dispersed across West Africa, and neighbouring tribes.

The Fulani, who migrated to the south to graze their cattle, claim farmers have tried to steal their animals and attack their people.

The gangs maintain camps in the Rugu forest, which straddles Katsina, Zamfara, Kaduna, and Niger states, from where they launch attacks.

Troop deployments and peace talks with local authorities have failed to end the attacks.

Unlike fighters belonging to the Boko Haram armed group, the criminal gangs have no ideological leanings, but concerns are growing the fighters are gradually infiltrating the gangs.

Earlier this year, the International Crisis Group warned the armed gangs could be developing links with groups such as ISIL in West Africa Province (ISWAP).

Criminal gangs have killed about 8,000 people since 2011 and forced more than 200,000 to flee their homes, according to estimates.