The Iraqi military, backed by the U.S., Kurdish forces and Iran-backed Shiite Muslim militias have reversed the militants' gains nationwide and begun a major military operation to take back Mosul.
However, rapid response units and police say that the fight in the Bab al-Tob area is expected to be tough because of the narrow streets through which armoured vehicles can not pass. The commandos of the Counter-Terrorism Service (CTS) continued their advance inside the neighbourhoods of Aghawat and Risala in the west of the old city centre.
A Shi'ite paramilitary spokesman said on Sunday a mass grave had been found containing the remains of "hundreds" of mainly Shi'ite inmates who were killed by Islamic State overran the Badush prison in June 2014.
AirWars, a UK-based non-profit monitoring the effect of anti-Isis air strikes on civilians, said last week that they believed 370 civilians died in US-led coalition bombing in just the first week of March alone.
In the Mansour district, from which Islamic State was driven several days ago, residents collected aid brought by volunteers from east Mosul while helicopters circled overhead, firing heavy machine guns and missiles at targets in the city.
The officials said Baghdadi likely left operational commanders behind in Mosul who will battle for control against Iraqi security forces.
In a 2014 report, Human Rights Watch said ISIS killed hundreds of prisoners, majority Shi'ites, when it seized Mosul that year.
"Our forces have seized control of 65 percent of western Mosul", he told Anadolu Agency.
Observers believe Islamic State militants have dug in deep there, knocking holes between adjoining buildings to allow them maximum mobility with minimum exposure to Iraqi and USA drones and aircraft.
USA officials believe that around half the 5,000 ISIS fighters in Mosul at the start of the offensive last October were killed or severely wounded.
Image copyright Reuters Image caption People leave the village of Badoush as the battle between Iraqi forces and IS intensifies Image copyright AFP/Getty Images Image caption Iraqi forces target IS positions near Badoush, some 15km (9.3 miles) northwest of Mosul What happened at the prison?
Removing the jihadis from Iraq's second largest city - which it has controlled since the summer of 2014 - will effectively spell the end of Isis, as a land-holding force in the country, driving the remnants of the group back to their de facto capital of Raqqa in neighbouring Syria. Iraqi Sunnis are disillusioned by the monopolization of power by a few Shia elite.