Isis prisoners escape
A Shi'ite fighter stands with his weapon in the town of al-Alam as Iraqi forces press ahead with anti-Isis offensiveThaier Al-Sudani/Reuters

Dozens of people held captive by the Islamic State (Isis) in Syria have managed to give the slip to the militants and escaped from a prison.

According to the Britain-based Syrian Observatory for Human Right, cited by Reuters, 95 people managed to escape the IS-run jail in al-Bab town in north Syria.

The nationalities of the escapees are unclear, while the Sunni insurgent group has kept the area on high alert following the prison break.

The incident took place in the town of al-Bab, which is located around 30kms south of Turkish border with Syria. The town has been witnessing intense infighting among IS militants and other local groups for the past few days leading up to the jailbreak.

The monitoring group said that those who fled the detention included several civilians and fighters belonging to other groups opposed to the IS.

Meanwhile, Iraqi forces accompanied by Shi'ite fighters have intensified their offensive against militants to recapture Tikrit.