Frustrated by guerrilla tactics from Islamic State militants, Iraqi forces paused for reinforcements on Friday, March 13 in a major offensive to take back the city of Tikrit, according to Reuters.

The operation appeared to have stalled for the time being, two days after Iraqi security forces and their mainly Shi'ite militia allies pushed into Tikrit, the home city of executed ex-president Saddam Hussein.

A source in the military command said Iraqi forces would not move forward until reinforcements reached Tikrit, of which Islamic State still holds around half.

If government forces wrest full control, it will be the first time they have won back a city from Islamic State since it over-ran large areas of the country last year and declared an Islamic caliphate in territory it is holding in Iraq and Syria.

From there it has spread fear across the region by beheading Arab and Western hostages and killing or kidnapping members of religious minorities like Yazidis and Christians.

In Tikrit, the militants have deployed snipers and turned streets into a labyrinth of home-made bombs and booby-trapped buildings.

Forces loyal to powerful Shi'ite cleric Moqtada al-Sadr and known as the 'Peace Brigades' appeared to be positioning themselves to join the government offensive. Up to 1,500 fighters had reached the sacred Shi'ite city of Samarra, south of Tikrit, a source in Sadr's provincial office told Reuters.

The deployment came days after Sadr announced the "unfreezing" of his forces' participation in battles against the militants. He had suspended their actions after allegations of abuses committed by other Shi'ite militias during recent operations.

One official said he was told that the Peace Brigade fighters intend to push north toward Tikrit on Saturday.

Hadi al-Amiri, the head of the Shi'ite paramilitary Badr Organization and now one of the most powerful men in Iraq, said the outcome of the battle for Tikrit was in no doubt, but Iraqi forces needed time.

"We are not in a hurry, but we have a plan and we are following it," Amiri told state television from the frontline. "Even if the battle drags on for two, three or four days that is okay. We will celebrate the liberation of Tikrit from the enemy.”