Nigerian military jets on Saturday bombed two camps in Isa district controlled by two gangs that have carried out deadly attacks on remote villages in recent weeks, the sources said.

This was the first such attack on bandits in the region.

But heavily armed gangs of cattle thieves and kidnappers for ransom known locally as bandits have terrorised northwest and central Nigeria for years, raiding and looting villages, and attacks have intensified in recent months.

"The military conducted aerial attacks on Tsaika and Dangwandi villages, where large numbers of bandits were killed," a local administrator in Isa district said.

"It is hard to say how many were killed but the toll is quite high as the camps were strewn with corpses of the bandits," said the local official who asked not to be named.

The fighter jets struck the two camps in simultaneous attacks, leading to large-scale "human and material damage to the terrorists," a security source in the region said.

"The two camps have been scorched and dead bodies and pulverized structures litter the camps," said the security source.

- 'Graduating into terrorists' -

The news of the attack was slow to emerge due to lack of telecommunication in the area. Both sources spoke from the state capital Sokoto, 80 kilometres (50 miles) away.

Troops have been conducting ground and air offensives on bandits camps in neighbouring Zamfara state since September, and bandits fleeing the operation there have moved into neighbouring Sokoto and Katsina states.

Authorities have shut down telecom infrastructure in Zamfara and parts of Kaduna and Katsina and Sokoto states to disrupt communication between the gangs.

The air strikes come in the wake of a series of deadly attacks in the region that the authorities have blamed on bandits.

On Monday 43 people were killed when bandits invaded two communities near the border with Niger, said officials.

In October, bandits killed 43 traders when they opened fire on a market in Goronyo.

On Monday Aminu Waziri Tambuwal, Sokoto state governor, warned bandits were "graduating into terrorists", echoing concern about growing ties between the criminal gangs and jihadist groups.

The gangs have increasingly turned to mass school kidnappings, having abducted more than 1,000 schoolchildren since last December.

While most of whom have been freed after ransom payments, others are still being held.