According to the ministry on Monday, the strikes inflicted heavy casualties on the ISIL, killing many of the Takfiri terrorists stationed in the embattled northern city in Salahuddin province.

The attack came a day after the commander of the Iraqi volunteer forces, Hadi al-Ameri, said that Iraqis do not need the US airstrikes in their operation to liberate Tikrit.

The army’s offensive marked the resumption of the Tikrit operation a week after Iraqi officials had announced its temporary halt to allow civilians to leave the embattled city.

"When we see that the time is right for the Tikrit alliance, we will storm in as quickly as possible," said Iraq’s Defense Minister Khaled al-Obeidi, adding, "Tikrit is under full siege. We are taking caution to not take any losses and to protect civilians in the city."

ISIL victims’ mass grave discovered

Earlier in the day, a mass grave was discovered in the town of Yathrib, about 170 kilometers north of the capital city of Baghdad.

An unnamed Iraqi security source said that the site contained the remains of Iraqi soldiers who had been murdered by ISIL terrorists.

The report, however, did not specify the exact number of the slain soldiers.

Tikrit operation

Earlier this month, some 30,000 Iraqi troops started a large-scale operation to recapture Tikrit, which is the birthplace of former Iraqi dictator Saddam Hussein. The volunteer forces, which include both Shia and Sunni members, also joined the operation.

Reports said the Iraqi army and volunteer forces regained much of Tikrit from the Takfiri militants following heavy firefight in the city.

Tikrit has a strategic position as it sits on the road to the ISIL stronghold, Mosul.

The ISIL terrorists, many of whom were initially trained by the US Central Intelligence Agency in Jordan in 2012 to destabilize the Syrian government, now control parts of Iraq and neighboring Syria. They have been engaged in crimes against humanity in the areas under their control.