Iraqi government forces attempted to evacuate civilians from Mosul’s ISIS-held Old City on Tuesday so that troops could clear the area.

The capture of the mosque would be a huge symbolic prize as well as strategic gain for the government as it was there where ISIS leader Abu Bakr al-Baghdadi declared the caliphate in July 2014 after the militants had captured large areas of Iraq and Syria.

Government forces backed by a US-led international coalition retook several cities last year, liberated eastern Mosul in December, and are now closing in on the west, but the militants are putting up fierce resistance from the close-packed houses and narrow streets.

Baghdadi and other leaders have fled the city for the hinterlands, where ISIS remnants may regroup and wage a new phase of insurgency. At the same time, ISIS forces in the Syrian city of Raqqa are under attack in a parallel conflict.

Brigadier General Saad Maan said soldiers had killed nine ISIS snipers on Tuesday and destroyed a bomb factory.

“There are lots of snipers on top of the buildings in the Old City around the al-Nuri Mosque. We need to evacuate the families from inside as they using them as a shield when we are advancing on the mosque,” he told the news conference.

No precise toll of civilian casualties has been given but a prominent Iraqi politician said last week that the number could be as high as 3,500 dead since the attack on western Mosul started in mid-February.

An emergency field hospital set up by the US medical charity Samaritan’s Purse says it has treated more than 1,000 patients, many of them women and children, since January. They suffered wounds from gunfire, land mines, mortar rounds, car bombings and booby-traps.

Reporters at the frontline on Tuesday said clashes took place around the railway station in some areas troops had held a few days earlier. Troops fired rocket-propelled grenades and heavy machineguns at militants around the station as families ran across streets to avoid snipers

“We sitting inside our house and bullets were coming through our door,” said one woman fleeing to government lines.