Police recaptured 21 of the escapees and imposed a curfew on the city as they looked for the rest, officials said.

Mosul, an al Qaeda stronghold located 390 km (240 miles) north of Baghdad in the troubled province of Nineveh, has seen a number of big prison breaks. Last year 23 prisoners convicted on terrorism charges escaped from the city’s Ghazlani prison.

In 2007, dozens of Al Qaeda-led militants stormed Badoush prison just outside Mosul and freed up to 140 prisoners. In December 2006, a nephew of Iraqi dictator Saddam Hussein escaped the same prison.

“This is the third incident taking place in Nineveh province of prisoners escaping ...There are dangerous leaders in the prisons, who need more intense (attention) from the security forces,” said Abdul-Raheem Al Shimeri, the head of the security committee in the Nineveh provincial council.

Violence has dropped dramatically in Iraq since the height of sectarian warfare in 2006-07 but shootings, bombings and other attacks happen daily.

Mosul is considered Iraq’s last urban stronghold of Sunni Islamist al Qaeda militants and much of the funding for the group’s attacks across the country is believed to come from Nineveh.

US forces are preparing to withdraw from Iraq by the end of the year, according to a bilateral security agreement.