Iraqi forces launched a final assault on Wednesday to capture the town of Hawija, one of two pockets of territory in Iraq still under the control of ISIS terrorist organization.

The Hawija operation’s commander, Lieutenant General Abdel Amir Yarallah, said the army, federal police and rapid response force had began a major operation “to liberate the center of Hawija and the neighboring town of Riyadh”.

Federal police chief Raed Shakir Jawdat said in a statement that the latest “phase of the operation to liberate Hawija” had begun with artillery and missile fire on militant positions.

Iraqi state TV broadcast live footage showing the Hawija area covered by thick black smoke, rising from oil wells torched by the militants as a tactic to prevent air detection.

Government and allied forces backed by a US-led coalition launched an offensive last month to oust ISIS from Hawija, a longtime insurgent bastion that is located near the oil city of Kirkuk, in northern Iraq.

The United Nations said on Tuesday that an estimated 12,500 people had fled the town since the launch of the offensive.

The UN’s humanitarian affairs office (OCHA) said the number of people still in the town was unknown but could be as high 78,000.

It said humanitarian agencies have set up checkpoints, camps and emergency sites in the area capable of receiving more than 70,000 people who could flee the Hawija operation.

The town is among the final holdouts from the territory seized by the terrorist group in 2014 and its recapture would leave only a handful of remote outposts in ISIS hands.

The other area of the country still under the control of the group is a stretch of land along the Syrian border, in western Iraq, including the border town of al-Qaim.

The militants also hold the Syrian side of the border at al-Qaim, but the area under their control is shrinking as they retreat in the face of two different sets of hostile forces – a US-backed, Kurdish-led coalition, and Syrian regime troops with foreign militias backed by Iran and Russia.