Iraqi forces have retaken more than 60 percent of eastern Mosul from the Islamic State group, a top commander said on Sunday.
The news comes as details emerge of IS tactics as fighting to recapture Iraq's second city intensifies.
"From east Mosul... more than 60 percent" has been recaptured from IS, Staff Lieutenant General Abdulwahab al-Saadi, a top commander in Iraq's Counter-Terrorism Service (CTS), told AFP.
The eastern side of Mosul, which is split by the Tigris River, is the larger of the two, but more civilians live in the west, he said.
Saadi said the militants have reinforced east Mosul, where the fighting has been concentrated so far, even using a crane to lift explosives-rigged vehicles across a destroyed bridge.
"The crane was struck," he said.
Iraq's highly-trained elite CTS forces on Saturday announced linking up with fellow elite unit Rapid Response Division to advance into western Mosul.
Forces more recently deployed inside the city have been moving house-to-house, dodging sniper fire, suicide car bombs and booby traps to retake one neighbourhood after another.
US coalition officials on Sunday defended striking near empty school buildings to destroy a mortar tube being used by IS militants to attack Iraqi security forces.
IS is known to use facilities such as mosques, hospitals and schools, all protected under the rules of international law, as weapons storage facilities, fighting positions and bases for its terrorist operations, the statement from Operation Inherent Resolve said.
"While the coalition takes extraordinary effort to protect civilians and strike appropriate military targets, we will continue to strike ISIL wherever and whenever our partner's lives are in danger in accordance with the Law of Armed Conflict," coalition officials added, using another acronym for IS.
Mosul is now the last Iraqi city where IS holds significant territory, but the extremists still control parts of western Anbar province and are able to mount frequent attacks in government-held areas, especially Baghdad.
Iraqi Prime Minister Haider al-Abadi had pledged that the city would be retaken by the end of 2016, a goal that was not realised.
He more recently stated that the country would need three months to eliminate IS - although that is still an ambitious timeline.