UN says aid workers readying for Mosul exodus

Aid workers in Iraq are preparing for a massive exodus of civilians from Mosul's Old City as Iraqi forces battle to retake the last district held by the Islamic State group.

UNHCR representative Bruno Geddo told AFP that aid groups need to be flexible during the fighting, with fears that tens of thousands of civilians are being held as human shields.

"There is a number of civilians still trapped in the Old City, they are basically used as human shields. Nobody is sure how many they are but it could be anything around 100,000, maybe more," he said late on Tuesday.

"We expect that eventually the cork may pop somewhere and we will have a large-scale outflow from the Old City."

Iraqi forces launched an assault to retake Mosul's Old City and push out the Islamic State group on Sunday, three years after the militants seized the city and announced their so-called "caliphate".

Taking back the Old City, a densely populated warren of narrow alleyways on the western side of Mosul, is crucial to recapturing the whole of the former IS bastion.

"I believe that this is a case of the largest urban warfare since World War II... so we have to be fast, to be flexible, to be ready to deal with the unpredictable," Geddo said.

Since the battle to retake Mosul began nine months ago, an estimated 862,000 people have been displaced from the city, although 195,000 have since returned, mainly to the liberated east of the city.

IS overran Mosul and swathes of Iraq and Syria in 2014, declaring a self-styled "caliphate" over areas it ruled.

The fall of Mosul was the worst defeat that Iraqi forces suffered in the war with IS, and regaining it would cap a major turnaround for security forces, who broke and ran despite outnumbering the militants who attacked the second city in 2014.