About 384 prisoners including militants escaped from a jail in northwestern Pakistan early on Sunday after an attack by insurgents armed with guns, grenades and rockets.

Officials said more than 150 militants stormed the central prison outside the restive northwestern town of Bannu bordering the lawless tribal regions where Taliban- and al-Qaeda-linked militants are active.

The attack began about 1am (local time) and continued for two hours, with militants in cars and utilities shooting and lobbing grenades to force their way into the prison, a security official told AFP.

"Some 384 prisoners, including some hardcore militants, have escaped during the attack," he said.

"Preliminary information suggests that there were some 944 prisoners in the jail according to the tally late Saturday."

Many militants had recently been moved to the jail from neighbouring Kohat and Lakki Marwat prisons, which are being converted into internment centres to rehabilitate former insurgents, the official said.

A former member of the air force sentenced to death for an attack on ex-president Pervez Musharraf was among the escaped militants, he said.

Police confirmed the attack but did not give any figures for the escapees, saying they were still investigating.

"There was an attack on the central jail and some prisoners escaped," senior Bannu police official Iftikhar Khan told AFP.

"At least three police officials were wounded in the attack."

The attackers outnumbered the security forces at the prison and militants fled before reinforcements reached the jail.

Another police official, Shafiq Ahmed, said security forces had imposed a cordon and a search operation was launched in the area.

"We have arrested four of the escaped prisoners," Ahmed told AFP.

- AFP