The reports, which were reported by some local media according to eye witness, come just days after the start of an operation led by the Iraqi army to retake the terrorist’s stronghold, IB Times reports.

Also Reuters reporting that ISIS militants have set fire to oil wells in the Ajil field east of the city of Tikrit to try to hinder aerial attacks aimed at driving them from the oilfield, a witness and military source said.

Black smoke could be seen rising from oil field since Wednesday afternoon, said the witness, who accompanied Iraqi militia and soldiers as they advanced on Tikrit from the east.

An engineer at the site told Reuters last July that Islamic State fighters were pumping lower volumes of oil from Ajil, fearing that their primitive extraction techniques could ignite the gas.

Bombing in August damaged the Ajil field's control room, according to the U.S. Energy Information Administration.

Some 30,000 Iraqi troops and militia, as well as military aircraft, began their biggest and toughest offensive yet on 2 March.

The battle raged between ISIS fighters and ground troops. Iraqi state-run TV stated on 4 March that government forces were advancing and recapturing oil fields.

Commanders from the Iraqi army were hoping that this operation would be the first of many, and a step towards re-capturing Mosul, the main ISIS stronghold in the country.

On Wednesday, the Ministry of Defense announced that 140 ISIS elements have escaped from the city of Tikrit, pointing out that about 30% of ISIS militants fled to Fallujah in al-Anbar.

The ministry said in a statement “Now the ISIS group is living in a state of anxiety, tension and breakage. Our members have spotted a mass escape of ISIS elements from the city of Fallujah, especially among the young fighters,” indicating that, “Approximately 30% has escaped the ISIS ranks so far.”

The ministry added, “Reports indicate that the number of militants fleeing from Tikrit has reached 140 terrorists, thanks to the successful military operations.”

A source in the leadership of Salahuddin operations reported that the security forces managed to liberate several areas in the north of Samarra, pointing to the progress towards the residential complex in Dour.

On the other side militants are employing guerrilla tactics -- everything from planting improvised explosives to hit-and-run attacks -- in an effort to impede Iraqi forces in their efforts to retake Tikrit.