At least 21 government militiamen were killed in an ambush by criminal gangs in Nigeria's northwest Katsina state, police said late on Friday.

A convoy of government militia returning from paying condolences to the family of a dead colleague came under fire from bandits in Baure, a village in the Safana district, Katsina police spokesman Abubakar Sadiq Aliyu said.

"Sadly, 21 persons were fatally shot as a result of the attack," Aliyu said, adding police were seeking to "ensure the arrest of the perpetrators" of the attack, which happened Tuesday.

Katsina is one of several states in northwestern and central Nigeria terrorised by bandits who raid villages, killing and abducting residents as well as burning and looting homes.

The gangs, who maintain camps in a huge forest straddling Zamfara, Katsina, Kaduna and Niger states, have earned notoriety for mass kidnappings of students from schools in recent years.

In 2023 Katsina state governor Dikko Umar Radda established Katsina Community Watch Corps (KCWC) comprising around 2,000 vigilantes to assist the military and police in fighting the gangs.