The slowdown highlights the challenges ahead for Iraqi forces as they press into more populated areas deeper in the city, where the civilian presence means they won't be able to rely as much on airstrikes.

"Their tactics include a lot of fortifications on the streets, holes filled with water, they have a lot of suicide bombers and suicide car bombs that they send toward us," said Lieutenant-Colonel of Iraqi army, Muhannad Saed.

Some civilians are fleeing the combat zone, while ISIS militants are holding others back for use as human shields, making it harder for Iraqi commanders on the ground to get approval for requests for US-led coalition air strikes.

"I just want to be safe. I don't have anybody, where should I go? Several days I have been homeless, me and my children, where should we go? I have no relatives and no tribe." Om Omar, Mosul resident said, "This and God will protect us," she added while holding the Quran.

Iraq's special forces are some of the country's best troops, but they still largely rely on air support to clear terrain. Iraqi forces first entered the eastern edge of Mosul on Tuesday.

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