Iraqi forces have captured 90 percent of the city of Tal Afar and are clearing it from ISIS militiants.
Iraqi military units, who have been battling in the last 7 days to drive ISIS from its bastion, said Saturday they had recaptured a large portion of the the city.
Earlier on Saturday military units reached the city centre and raised the country's flag atop its Ottoman-era citadel.
"Units of the Counter-Terrorism Service liberated the Citadel and Basatin districts and raised the Iraqi flag on top of the citadel," operation commander General Abdulamir Yarallah said in a statement.
The CTS and federal police units had converged on the city centre from the south and west, said General Yarallah.
Clashes were ongoing on the northern outskirts and Iraqi forces were dealing with the final pockets of resistance inside the city, he added.
Saturday's advance puts Iraqi forces on the verge of recapturing Tal Afar only six days after they launched an offensive to take back one of the last ISIS strongholds in the country.
It follows weeks of Iraqi and US-led coalition air strikes.
Tal Afar is located 70 kilometres (40 miles) west of Mosul, where the militant group declared its "caliphate" in 2014 before being ousted from the city in July.
Iraqi forces on Saturday also seized three northern districts of Tal Afar and the Al-Rabia neighbourhood west of the citadel, a day after taking the Al-Talia district to the south.
Tal Afar, which had 200,000 residents until ISIS captured it in a 2014 offensive, is on a strategic road that linked ISIS-held territories in Syria with Mosul.
Once Tal Afar is retaken, Baghdad is expected to launch a new offensive on Hawija, 300 kilometres north of Baghdad.
ISIS also present in the vast western province of Anbar, where it controls several zones along the Syrian border with war-ravaged Syria, including the Al-Qaim area.
The militant group has lost much of the territory it controlled and thousands of its fighters have been killed.