Boko Haram crisis: Nigeria raids 'kill militants'

(BBC) - An unknown number of militants have been killed during air raids on their training camps in north-eastern Nigeria, officials say.

The army spokesman said jets and helicopter gunships had been used to attack several camps.

The raids came after states of emergency were declared in three north-eastern states hit by Boko Haram's Islamist insurgency.

Meanwhile, explosions and gunfire have been heard overnight in Katsina state.

Residents have told the BBC's Hausa service that banks, police stations and prisons were destroyed in the town of Daura, near the border with Niger.

They said they had seen the bodies of five members of the security forces and three militants, but there has been no official confirmation of casualties.

Mobile phone networks were not functioning in many parts of north-east Nigeria on Thursday.

A security official told the AP news agency that the mobile phone service had been shut down during the military operation.

Militants have previously attacked mobile phone masts in the area in an effort to disrupt communications.