A group of local vigilantes were struck over the weekend as they were pursuing a criminal gang in Zamfara state, the residents said.

The Nigerian army did not immediately respond to a request for comment.

The incident is the latest in an air campaign that has killed hundreds of civilians in recent years as Nigeria battles various armed groups, from jihadists to criminal gangs known as "bandits".

The bandits had attacked Mani and Wabi villages in Maru district, stealing cattle and kidnapping dozens of people, residents told AFP.

Residents of nearby Maraya village and neighbouring communities mobilised and launched a pursuit to free the hostages and the cattle, according to locals.

But a military jet which deployed to assist the community after people in the area alerted security personnel mistook the volunteers for the bandits and bombed them between Maraya and Wabi, the sources said.

"We were hit by double tragedy on Saturday. Dozens of our people and several cows were taken by bandits and those who trailed the bandits to rescue them were bombed by a fighter jet. It killed 20 of them," resident Buhari Dangulbi said.

Bandits have wreaked havoc for years in Nigeria's northwest, operating in broad swathes of relatively ungoverned countryside. Unlike their jihadist counterparts in the northeast of the country, their motivations are primarily economic.

Military bombing campaigns against both bandits and jihadists have proven deadly for civilians caught in the crossfire. The incident Saturday was the third such to occur in Zamfara state.

Amnesty International Nigeria called on Nigerian authorities to "transparently investigate" the incident.

"Attacks by bandits clearly warrant a response from the state, but to launch reckless air strikes into villages -- again and again -- is absolutely unlawful," the rights group said in a post on X.

Describing the scene, another resident Ishiye Kabiru, who also gave a toll of 20 dead, told AFP: "Our vigilantes from Maraya and nearby communities gathered and went after the bandits. Unfortunately, a military jet struck them."

A third resident, Alka Tanimu said, gave the same toll, with similar details, noting "we will still have to pay to get those kidnapped back while the cows are gone for good".

- Hundreds killed over the years -

In January, at least 16 people were killed in a military airstrike after a jet mistook local vigilantes for criminal gangs terrorising communities in Zurmi district of Zamfara state.

In December 2022, more than 100 civilians were killed when a jet pursuing fleeing bandits bombed Mutunji village in Zamfara's Dansadau district.

In December last year, 10 people were killed and six others injured when a jet hit two villages while bombing the position of Lakurawa jihadists in Sokoto state.

In December 2023, a Nigerian military airstrike mistook a religious gathering of Muslim faithful for bandits in Tudun Biri community in northwestern Kaduna state, killing at least 85, mostly women and children.

In January 2017, at least 112 people were killed when a fighter jet struck a camp housing 40,000 people displaced by jihadist violence in the town of Rann near the border with Cameroon.