Iraqi security forces have seized control of more than one-third of western Mosul after a week of steady gains in their battle to retake the ISIL-held city where 600,000 civilians are trapped.
Staff Major-General Maan al-Saadi of Iraq's elite Counter-Terrorism Service told AFP news agency on Sunday about 17 of 40 western districts of the second-largest city had been retaken from Islamic State of Iraq and the Levant (ISIL).
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It was not possible to independently confirm the claim.
"The enemy has lost its fighting power and its resolve has weakened. It has begun to lose command and control," said Saadi.
He said his forces were fighting ISIL - also known as ISIS - inside the Mosul al-Jadida and al-Aghawat areas on Sunday.
Iraq's joint operations command said another special forces unit and federal police were attacking the Bab al-Toub area on the edge of Mosul's Old City.
"The battle is not easy ... We are fighting an irregular enemy who hides among the citizens and uses tactics of booby-trapping, explosions, and suicide bombers, and the operation is taking place with precision to preserve the lives of the citizens," said Brigadier-General Yahya Rasool.
Later on Sunday, Brett McGurk, the US envoy to the anti-ISIL coalition, said the remaining western Mosul neighbourhoods held by the group were completely surrounded by Iraqi forces.
ISIL "is trapped. Just last night, the 9th Iraqi army division, up near Badush, just northwest of Mosul, cut off the last road out of Mosul," he said.
"Any of the fighters who are left in Mosul, they're going to die there, because they're trapped. So, we are very committed to not just defeating them in Mosul, but making sure these guys cannot escape."
McGurk said that ISIL had already lost more than 60 percent of the territory it once held in Iraq.
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As many as 600,000 civilians are trapped with ISIL fighters inside west Mosul.
More than 65,000 people have been displaced by the fighting in the past two weeks, bringing the total number to more than 200,000 since the campaign to recapture Mosul began last October, according to the International Organisation for Migration.
ISIL seized Mosul in mid-2014 when the group swept across areas north and west of Baghdad, taking control of swaths of territory and declaring a cross-border "caliphate" in Iraq and neighbouring Syria.
Backed by US-led air strikes and other military support, Iraqi forces have since retaken much of the territory they lost.
Losing Mosul would be a major blow to ISIL, but the group is expected to pose a continuing threat, reverting to guerrilla-style tactics such as bombings.
Source: News agencies