The prisoners are said to have escaped through a window space half a metre square.

The break-out is not the first time al-Qaeda members have escaped from jail, suggesting the prisoners received outside assistance.

Al-Qaeda are believed to pay up to $20,000 for someone who can help to free their senior leaders from jails.

A curfew was imposed on the city after the escape, which occurred on Wednesday night.

Authorities are distributing wanted posters with photos of the fugitives and are running checkpoints around Tikrit, the hometown of Saddam Hussein, the deposed Iraqi leader.

The city is about 130km north of Baghdad, the Iraqi capital.