GENEVA (Reuters) - About 100,000 civilians remain trapped behind Islamic State lines in Mosul with a U.S.-backed government offensive to recapture the Iraqi city entering its ninth month, the United Nations refugee agency UNHCR said on Friday.

The army's 16th infantry division captured Hadarat al-Saada and al-Ahmadiyya, northwest of the historic Grand al-Nuri Mosque which the militants destroyed last week. Islamic State still controls the mosque's grounds and about half of the last territory it runs in the Old City.

During the last eight months, Iraqi forces have fought to corner Islamic State militants into an ever-dwindling area of the city of Mosul. Troops this week began the long-anticipated assault on the Old City quarter, the last district still in the extremist group's hands. And Wednesday, officials said militants destroyed the iconic Nuri mosque, the site where Islamic State leader Abu Bakr Baghdadi declared the group's caliphate three years ago. As the pressure has increased around Mosul since the government offensive to retake it began Oct. 17, the fight has apparently transformed into a so-called cauldron battle, where the militants have no chance of escape. Their only options would be to surrender or die.

During the last eight months, Iraqi forces have fought to corner Islamic State militants into an ever-dwindling area of the city of Mosul. Troops this week began the long-anticipated assault on the Old City quarter, the last district still in the extremist group's hands. And Wednesday, officials said militants destroyed the iconic Nuri mosque, the site where Islamic State leader Abu Bakr Baghdadi declared the group's caliphate three years ago. As the pressure has increased around Mosul since the government offensive to retake it began Oct. 17, the fight has apparently transformed into a so-called cauldron battle, where the militants have no chance of escape. Their only options would be to surrender or die.

An Iraqi Special Forces sniper watches Islamic State positions as Iraqi forces continue their advance in the Old City of Mosul, Iraq, Wednesday, July 5, 2017. An Iraqi Special Forces sniper watches Islamic State positions as Iraqi forces continue their advance in the Old City of Mosul, Iraq, Wednesday, July 5, 2017. Iraqi Special Forces soldiers walk to the frontline as Iraqi forces continue their advance against Islamic State militants in the Old City of Mosul, Iraq, Wednesday, July 5, 2017. Iraqi Special Forces soldiers walk to the frontline as Iraqi forces continue their advance against Islamic State militants in the Old City of Mosul, Iraq, Wednesday, July 5, 2017.