BAGHDAD (Reuters) - Iraqi forces have fought their way into two more southeastern districts of Mosul but their advances are being slowed by Islamic State's tactic of using civilians for cover, a military spokesman said on Tuesday.
The United Nations said civilian casualties had streamed into nearby hospitals in the last two weeks as fighting intensified in the jihadist militia's last major stronghold in Iraq.
Advances by elite forces in the city's east and northeast have picked up speed in a new push since the turn of the year, and U.S.-backed forces have for the first time reached the Tigris river, which bisects the city.
But fighting in neighborhoods in the southeast has been tougher.
"The challenge is that they (IS) are hiding among civilian families, that's why our advances are slow and very cautious," Lieutenant-Colonel Abdel Amir al-Mohammedawi, a spokesman for the rapid response units of Iraq's federal police, told Reuters.
He said rapid response units and Iraqi army units had fought their way into the Palestine and Sumer districts in the last day, but that Islamic State fighters were firing at civilians trying to flee.
"The families, when they see Iraqi forces coming, flee from the areas controlled by Daesh (Islamic State) towards the Iraqi forces, holding up white flags, and Daesh bomb them with mortars and Molotov cocktails, and also shoot at them.
"Whenever they (IS) withdraw from a district, they shell it at random, and it's heavy shelling," he said.
The United Nations' humanitarian coordination office (OCHA) said nearly 700 people had been taken to hospitals in cities in Kurdish-controlled areas outside Mosul in the last week, and more than 817 had required hospital treatment the week before that.
"Trauma casualties remain extremely high, particularly near frontline areas," it said.
The U.S.-backed operation to drive the ultra-hardline militants from Mosul began in October and has recaptured villages and towns surrounding the city, and most of Mosul's eastern half.
New tactics and better coordination have helped Iraqi forces advance faster since they launched a new phase of the operation more than 10 days ago.
The advances slowed in November and December as IS put up fierce resistance and hid among the civilian population, making it difficult for Iraqi forces to target them.
(Reporting by John Davison; Editing by Kevin Liffey)