Iraqi forces besieging dozens of die-hard fighters of the Islamic State of Iraq and the Levant (ISIL) in Tikrit will have liberated the city within three days, a spokesman said.

Karim al-Nuri, a top leader from the Badr militia and the spokesman of the volunteer Popular Mobilisation units, said on Saturday it would take no more than "72 hours" to flush out holdout IS fighters.

The Popular Mobilisation units account for the bulk of the manpower involved in the two-week-old offensive to wrest back Tikrit, alongside army, police, militia and tribal forces.

The last IS fighters holed up in the city centre are "surrounded from all sides", Nuri said.

Speaking to the AFP news agency from the outskirts of Tikrit, near the village of Awja, he said "their number is now 60 to 70".

Nuri added that the liberation of Tikrit would only be announced once a path has been cleared through the thousands of bombs the jihadists have planted to defend the city.

Offensive halted 

Nuri's comments came as the Reuters news agency reported that Iraqi forces and mainly Shia militia battling ISIL had paused their offensive for a second day on Saturday as they awaited reinforcements.

A source in the local military command centre told Reuters military commanders had "reached a decision to halt the operation until a suitable, carefully set plan is in place" to break into central Tikrit.

The source, speaking by phone from near Tikrit, said the Iraqi forces and Iranian-backed Shia militias known as Popular Mobilisation were waiting for reinforcements from "well-trained forces". He did not give a timeline for the arrival of the reinforcements.

"We do not need a large number, just one or two thousand. We need professional personnel and soldiers," he said, explaining they were needed to engage in street-by-street battles with ISIL fighters who have booby trapped many buildings in the city and laid improvised explosive devices and roadside bombs.

Army and militia forces pushed into Saddam Hussein's home city on Wednesday in their biggest drive yet against the fighters who seized large swathes of land in Iraq and neighbouring Syria last year in a lightning campaign halted just outside Baghdad.

More than 20,000 troops and allied militias entered the city about 160km north of the capital after retaking towns to the south and north in a campaign launched nearly two weeks ago.

Source: Agencies