TAL AFAR AIRBASE — Iraqi forces closed in Monday on Tal Afar on the second day of an offensive against the last major bastion of Daesh (the so-called IS) group in the country's north, after seizing several villages around the city.

The offensive launched at dawn Sunday comes only weeks after Iraqi forces seized second city Mosul from Daesh and as the militants also face assaults on their positions in Syria.

Tal Afar was once a major supply hub between Mosul and the Syrian border and capturing it would be another major blow to Daesh's self-declared "caliphate" that once controlled large parts of Syria and Iraq.

The Iraqi army, federal police and counter-terrorism forces backed by 20,000 fighters from the Hashed Al-Shaabi paramilitary group launched the offensive on Tal Afar.

They are battling Daesh on three fronts — the west, south and southeast — and commanders have told AFP they expect to tighten the noose on the militants by edging closer to the gates of the city.

The federal police said its forces had retaken four villages on the western front on the first day of the operation while the Iran-backed Hashed said its fighters had advanced to the edges of Tal Afar's western suburbs.

Iraqi forces have been pounding Daesh with mortar fire after weeks of air strikes to weaken the fighters who overran Tal Afar in 2014.

In an indication of their next target, Iraqi planes on Sunday and Monday dropped leaflets on the town of Hawijah to the south, urging residents to prepare as "retaking your city is the next goal of the armed forces".

Hawijah in Kirkuk province is some 300 km northwest of Baghdad.

The militants also still hold areas of the vast western desert province of Anbar, including the Al-Qaim area on the border with war-ravaged Syria.

The battle for Tal Afar, the last major population centre in northern Iraq under militant control, has sparked fears for thousands of civilians trapped inside.

The US-led coalition fighting Daesh in Iraq and Syria says between 10,000 and 50,000 civilians are estimated to be in and around Tal Afar.

UN Humanitarian Coordinator for Iraq Lisa Grande said Sunday that "more than 30,000 people have already fled" the Tal Afar region and that thousands more were expected to follow.

"Families are trekking for 10 to 20 hours in extreme heat to reach mustering points. They are arriving exhausted and dehydrated," Grande said in a statement.

"We don't know how many civilians are still in the areas where fighting is occurring, but we are preparing for thousands more to flee in coming days and weeks."

When Daesh captured Tal Afar, the population was estimated at around 200,000 and was overwhelmingly Turkmen, one of Iraq's largest ethnic minorities. — AFP