Iraqi officers have said snipers have slowed them down in western Mosul in the biggest ground operation in Iraq since the 2003 US-led invasion that toppled Saddam Hussein.
US -backed Iraqi forces are now battling IS militants in Mosul and more than half of western Mosul has been retaken.
Iraqi forces have been making "incremental progress" in their fight to retake west Mosul as ISIS has increased its use of human shields in their last stand.
The battle for Mosul, one of Iraq's largest cities, began last October and the outcome will likely determine whether Iraq's various sects can work together to keep the country from fracturing.
"Under global humanitarian law, parties to the conflict are obliged to do everything possible to protect civilians and limit damage to civilian infrastructure".
"The Syrian Democratic Forces and their Syrian-Arab coalition continue advancing as they further isolate Raqqa city", Dorrian said. Security forces have faced a painstaking job of clearing the city of ISIS while trying to avoid civilian casualties.
A top "mufti" of the Daesh terrorist group was killed by Iraqi police in western Mosul, a high-ranking police official said Friday.
Losing Mosul would be a major blow to IS, but would not mark the end of the war against the jihadists.
"We will not leave any area under the control of the terrorist organisation", Brigadier General Yahya Rasool, the spokesman for Iraq's Joint Operations Command, said at a recent news conference.
It was unlcear whether the bridges had become submerged or damaged by the floods, but soldiers blocking the approach roads said they were unusable.
Losing these areas would still not eliminate the threat of bombings and hit-and-run attacks by the jihadists.
Iraqi "successes in Mosul obscure how (IS) has successfully been resurging in other provinces in Iraq", Martin said.
This week 18 Syrian fighters allied with the USA were struck and killed on Thursday by an American-led coalition aimed to attack the Islamic State.