Iraqi forces killed 25 operatives of the so-called ’Islamic State of Iraq and the Levant’ (ISIL) takfiri group on Tuesday in the northern province of Salahuddine.

Iraqi forces killed 25 operatives of the so-called 'Islamic State of Iraq and the Levant' (ISIL) takfiri group  on Tuesday in the northern province of Salahuddine, an army spokesman said, stressing that strategy for retaking the Tikrit is to surround the city before launching the assault.

A senior commander said operations were currently focused on preventing ISIL from launching more attacks and cutting supply lines to stop reinforcements and weapons from reaching Tikrit.

Speaking to AFP, Lieutenant General Abdul Amir al-Zaidi said that the next step will be to "surround the towns completely, suffocate them and then pounce on them."

He said the operation launched Monday had already achieved results by securing areas further out in Salaheddin province and forcing ISIL terrorists to regroup in urban areas.

Al-Jabbour tribal group and the al-Hashid al-Sha’bi (popular crowds) supported the Iraqi troops during the clashes, which took place near the city of Tikrit.

Karim al- Nouri al-Hashid, the al-Sha’bi Shiite militia’s spokesman says "Most of the killed ISIL members were Arab nationals not Iraqis. The majority of the militants retreated to central Tikrit."

On Monday, the Iraqi security forces and a variety of allied fighting units launched the biggest ground operation yet against ISIL in Iraq.

Backed by jets and helicopters, the 30,000-strong force is moving in from three main directions, their progress slowed by suicide bombers, sniper fire and booby traps, Zaidi said.