A suicide bomber blew himself up on Friday (June 23rd) among civilians fleeing Mosul's Old City, where Iraqi forces are gaining ground against extremists mounting a fierce but desperate defence, officers said.

Ahmed Hashem, a major and medic in the Iraqi army speaking to AFP from a field hospital, said the attack took place in the Mashahda neighbourhood of the Old City.

"We received 12 people killed and more than 20 wounded in our field hospital, including women and children," he said.

A colonel in the army's 16th infantry division said it was difficult to get a definitive casualty toll because the area where the attack happened was not fully cleared.

"The suicide bomber infiltrated a group of displaced people and blew himself up among them before reaching our troops," he said.

Thousands of civilians have fled the Old City of Mosul since Iraqi forces launched their most perilous assault yet against the "Islamic State of Iraq and Syria" (ISIS).

Around 100,000 more remain trapped by the extremists, who have made human shields a key element in their defence of the Old City.

The security forces have been wary of Iraqi ISIS members attempting to flee the Old City death trap by blending in with the population, while the Chechen, French and other foreign fighters stay behind to mount a suicidal last stand.

But on Friday, Prime Minister Haider al-Abbadi said it is a matter of days before Mosul falls back into Iraqi forces' hands.

"The announcement of the end of ISIS in Mosul will be a major victory, and it will be realised within days," al-Abbadi said in a statement following a meeting with top Iraqi army officers and commanders who are overseeing the liberation of Mosul.

"ISIS elements are besieged. They will be either killed or arrested as they are running out of ammunition," Federal Police Chief Lt. Gen. Raed Shaker Jawdat told Diyaruna.