The military operation and communications blackout in Zamfara state came after gunmen kidnapped more than 73 school students in the latest mass abduction by heavily-armed criminals known locally as bandits.

On Saturday, military jets began air raids on remote camps of gangs and troops moved after the authorities imposed a telecommunication shutdown aimed at disrupting contacts and coordination between the gunmen.

"Several camps have been raided, a large number of the bandits have been neutralised," said a security source with knowledge of the operations.

"The bandits are feeling the heat and are in disarray while troops pursue them," said the source, who asked not to be identified.

A second security source confirmed bandit camps had been targeted by air and ground offensives since Saturday.

The operation continued on Monday for the third day, targeting bandit camps dotting Sububu forest in Shinkafi district, the sources said.

Northwest and central Nigeria have for years struggled with tit-for-tat violence between local farmers and nomadic herders whose clashes over land and water have escalated.

Violence has worsened with the emergence of criminal gangs, often with hundreds of members, who raid communities, steal cattle and kidnap residents for ransom after looting and burning homes.

The bandits' heavily-guarded camps dot the Rugu forest, straddling the northern states of Kaduna, Katsina Zamfara and Niger, where they often hold their kidnap victims for weeks and months.

The gangs have recently intensified attacks on schools where they haul off students to squeeze payments from authorities and parents.

On Wednesday bandits seized 73 students of a secondary school in Zamfara's Maradun district. Around 1,000 students have been taken in similar raids since December, though most were released after negotiations.

On Friday, Nigeria's telecom regulator ordered operators to shut down their towers in Zamfara state for two weeks, following request from the state authorities.

Local authorities complained the bandits were using phones to coordinate among themselves and get information about troop movements from informants in neighbourhood communities.

Attempts to contact Zamfara officials were unsuccessful because of the shutdown and news on the military operation was scarce.

Bube Altine, a grains trader from Shinkafi confirmed the military operations to AFP, saying fighter jets had been flying in the area since Saturday.

"Soldiers are in the forest and jets have been flying overhead but nobody can say what is happening," Altine said.

He was attending a weekly market in Jibia town in neighbouring Katsina State when he spoke to AFP.

Several states in northwest Nigeria have introduced restrictions on motorcycle traffic, cattle trading and fuel sales -- all measures aimed at curtailing bandit movement and activities.