(This July 6 story has been refiled to remove extraneous material from quote by MSF member, in 13th paragraph.)

A tank of the Emergency Response Division fires at Islamic State militant in the old city of Mosul, Iraq July 5, 2017. REUTERS/Alaa Al-Marjani

GENEVA/ERBIL, Iraq (Reuters) - The population of Mosul has endured huge suffering in the war to retake the northern Iraqi city from Islamic State and trauma cases among civilians are sharply rising in the last stages of battle, Doctors Without Borders (MSF) said on Wednesday.

The city’s basic infrastructure has also been hard hit, with six western districts almost completely destroyed and initial repairs expected to cost more than $1 billion, the United Nations said.

Tens of thousands of civilians remain trapped among the shattered buildings in Islamic State’s final redoubt in Mosul’s Old City by the western bank of the Tigris river, MSF said.

Civilians who have managed to get medical treatment are suffering from burns and shrapnel and blast injuries, while many are in need of critical care and are under-nourished, MSF officials said.

But there is concern that only a small number of the civilians were getting the medical attention they required.

“Really, (there is) a huge level of human suffering,” Jonathan Henry, MSF emergency coordinator in west Mosul, told reporters in Geneva after spending six weeks in Iraq.

“This is a massive population that has been traumatized from a very brutal and horrific conflict,” he said.

Iraqi commanders have predicted final victory in Mosul this week after a grinding eight-month assault that has pushed Islamic State into a rectangle no more than 300 by 500 meters in the city whose population used to be 2 million.

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International charity Save the Children said in a separate report that fighting and years of living under Islamic State have left Mosul’s children with dangerous levels of psychological damage.

Findings from focus group discussions with 65 children in a displacement camp south of Mosul found that children are so deeply scarred by memories of extreme violence they are living in constant fear for their lives, unable to show emotions, and suffering from vivid “waking nightmares”.

The loss of loved ones was the biggest cause of distress, with 90 percent reporting the loss of at least one family member through death, separation during their escape, or abduction, the report said.

Children said they had seen family members killed in front of them, dead bodies and blood in the streets, and bombs destroying their homes. Others shared stories of family members shot by snipers, blown up by landmines or hit by explosions as they fled.

In short, Mosul is an “extremely traumatic environment for people to flee from and to return to,” affecting their mental health on a large scale, MSF’s Henry said.

“The west (of the city) has been heavily destroyed. It’s really mass destruction ... similar to the blitz of the Second World War, hospitals have been destroyed, neighborhoods are in ruins.”

The battles in the Old City’s maze of narrow alleyways is fought house-by-house in streets packed with civilians and planted with multiple explosive devices by the militants, who are also using drones and suicide bombings.

Shrapnel and blast injuries, broken bones from collapsed buildings and burns are the main type of wounds seen by the MSF team of surgeons in west Mosul, Henry said.

Half of the 100 war-wounded over the past two weeks at the MSF 25-bed hospital were women and children in need of critical care and many were malnourished, he said.

“But the most urgent patients we feel are not able to leave the conflict area.”

About 900,000 people have been displaced by the fighting, taking shelter in camps or with relatives and friends, according the aid group.