Iraqi and coalition warplanes carried out air strikes Tuesday against ISIS targets in Tal Afar in preparation for a ground offensive to retake the northern town near the Syrian border, the military said. "Preparations are under way pending instructions from the commander in chief (Prime Minister Haider al-Abadi)" for the launch of the assault, said a spokesman for Iraqs Joint Operation Command (JOC). Although the main offensive to retake Tal Afar had not yet begun, the air force was pounding militant positions in the town, the spokesman, Yahiya Rassul, said. A series of airstrikes this week targeted ISIS headquarters, tunnels and weapons stores, Iraqs air force commander Lt. Gen. Anwar Hama told The Associated Press. Tal Afar is the main remaining ISIS stronghold in northern Iraq, after the capture by Iraqi forces in July of second city Mosul further east in a major blow to the terrorist group. Plans to retake Tal Afar were announced on Monday by federal police chief Lieutenant General Raed Shakir Jawdat, who said "armored and elite units" were headed for the town. The units, whose number has not been specified, were "regrouping in combat positions in preparation for the next battle," he said in a statement. Joining them are the Popular Mobilization Forces (PMF). “PMF commanders met Saturday with army and police commanders to decide on the plan to free Tal Afar," spokesman Ahmed al-Assadi said. Abadi is expected to announce the launch of the ground assault but there are no indications on when it is due to start. ISIS overran Tal Afar in June 2014, when it had a population of around 200,000. Since April, the United Nations says some 49,000 people have fled the Tal Afar district. Families who have escaped across front lines describe dire humanitarian conditions inside the town, with water and food supplies dwindling. According to the UN, over the course of the nine-month operation to retake Mosul and surrounding villages, nearly a million people were displaced.