The US military helped Iraqi authorities in the search for the escaped prisoners with various surveillance [EPA]

Fourteen prisoners charged with "terrorism" escaped from a prison via a tunnel in the northern Iraqi city of Mosul, security officials say.

Jailbreaks and prison unrest are relatively common in Iraq.

"Thirty-five prisoners tried to escape from a prison in Al-Faisaliyah" in central Mosul, Colonel Mohammed al-Juburi, of the Nineveh province police in Mosul, said on Thursday.

Security forces "arrested 21 of them, but 14 others were able to escape from the prison", he said.

All 35 inmates were charged with terrorism-related offences, he said.

Al-Juburi said that an open-ended curfew was imposed in Mosul at 05:00 GMT on Thursday due to the jailbreak.

Colonel Rahim al-Shammari, spokesman for Nineveh police, said later on Thursday that the prisoners who escaped did so via a tunnel under the prison that was about 50 metres long.

Al-Juburi had said earlier that no clashes took place during the escape.

However, Mohammed Salem said that City Hospital, where he works in Mosul, had received two prisoners with bullet wounds to their legs.

Ministry confirmation

A police source said that the wounded prisoners were among the 21 arrested trying to escape.

An interior ministry official confirmed that 35 prisoners had attempted to escape in Mosul, but that 21 of them were apprehended.

The US military helped Iraqi authorities in the search for the escaped prisoners with helicopters and other surveillance aircraft, according to Colonel Brian Winski, commander of 4th Advise and Assist Brigade, 1st Cavalry Division.

The inmates who escaped were Iraqis from low-level cells with links to al-Qaeda's affiliate, Winski told reporters in Washington via video link from Iraq.

"None of them were foreign fighters. None of them were high-level leaders," Winski said.

The prison was a "transit detention facility" and not a site where inmates were held over a long period, he said.

"The search is still on for those few that do remain at large, and I'm quite confident, again, with some assistance from us, that they will find them," he said.

Officials said on August 6 that four prisoners and a guard were killed in clashes at a prison in the central Iraqi city of Hilla, during which eight inmates escaped.

Six Iraqi police and 11 inmates were killed in a Baghdad jail mutiny in May, while 12 suspected al-Qaeda members escaped from prison in the southern city of Basra in mid-January. At least two of the Basra escapees have been recaptured.