Iraqi Forces Battle toward Landmark Mosul Mosque

The close-quarters fighting is focused on the Old City surrounding the mosque where Daesh leader Abu Bakr al-Baghdadi proclaimed a caliphate nearly three years ago across territory controlled by the group in both Iraq and Syria.

Thousands of residents have fled from Daesh-held areas inside Mosul, the terrorists' biggest remaining stronghold in Iraq. But tens of thousands more are still trapped inside homes, as Iraqi forces advance in the west.

Helicopters circling west Mosul strafed Daesh positions beyond the city train station, the site of heavy back-and-forth fighting in recent days, and thick black smoke rose into the sky, Reuters reporters on the ground said.

Heavy sustained gunfire could be heard from the Old City area, where terrorists are hiding among residents and using the alleyways, traditional family homes and snaking narrow roads to their advantage, fleeing residents say.

"Federal police forces have imposed full control over the Qadheeb al-Ban area and the al-Malab sports stadium in the western wing of Old Mosul and are besieging militants around the al-Nuri mosque," federal police chief Lieutenant General Raed Shaker Jawdat said in a statement.

Rapid Response elite interior ministry troops were advancing on the edge of the Old City, clambering over garden walls. Daesh responded with rocket fire, streaking the sky with white smoke plumes.

"There are teams going into the Old City since yesterday," said Rapid Response official Abd al-Amir.

Iraqi troops shot down at least one suspected Daesh drone. The terrorists have been using small commercial models to spy and drop munitions on Iraqi military positions.

With the battle entering the densely populated areas of western Mosul, civilian casualties are becoming more of a risk. The United Nations says several hundred civilians have been killed in the last month, and residents say Daesh militants are using them as human shields.

The senior US commander in Iraq acknowledged on Tuesday that the US-led coalition probably had a role in an explosion in Mosul believed to have killed scores of civilians, but said Daesh could also be to blame.

As investigators probe the March 17 blast, Lieutenant General Stephen Townsend said increases in casualties were to be expected as the war against the insurgents entered its deadliest phase in the cramped, narrow streets of Mosul's Old City.

Local officials and eyewitnesses say as many as 240 people may have been killed in the Al-Jadida district when a huge blast caused a building to collapse, burying families inside. Rescue workers are still pulling bodies out of the site.