Over the past 24 hours, around 150 ISIL extremists, including commanders, reportedly left Tikrit, the birthplace of late Dictator Saddam and a stronghold of the group. Iraqi forces managed to take eastern and southern parts of the town under control.

The assault, which started on Monday, is Iraqi troops' largest military campaign so far in 2015. The joint forces of the Iraqi army and volunteer Shia militia make up around 30,000 people. A victory in Tikrit would allow the army to move on Mosul, Iraq's second largest city, controlled by the ISIL since last summer.

During the first stage of the offensive, Iraqi forces, supported from the air by jets and helicopters, encircled oil fields east of Tikrit and blocked the road leading to Mosul.

The Iraqi Army, backed by allied fighters, reportedly captured villages and oil fields east of the ISIS-held city of Tikrit on Wednesday, cutting off a key supply route for the militants.

A military source told the BBC that Iraqi forces have taken control of the village of al-Maibdi, on the road to the Kurdish-controlled city of Kirkuk, and the nearby Ajil and Alas oil fields. The road is a key supply route for ISIS between the Salahuddin and Diyala provinces, the source added.