Iraqi forces, supported by US-led airstrikes and special forces, advanced on Mosul from the east and the south on Monday in the first phase of a long-planned offensive to retake the city from Islamic State.

The advance on Monday evening aims to liberate Iraqs second biggest city, an Isis stronghold where its leader, Abu Bakr al-Baghdadi, declared the establishment of a caliphate two years ago.

The Kurdish forces, known as peshmerga, advanced steadily in long armoured columns across the Nineveh plain to the east of Mosul, pausing at each deserted village to allow engineers to search for mines and booby traps left by Isis.

Peshmerga officials claimed their tanks had destroyed two Isis suicide truck bombs. By the end of the first day in the attempt to oust the jihadi group from their last major Iraqi stronghold, Kurdish leaders said their forces had captured 200 sq km (77 sq miles).

Most of the local population on the Nineveh plain has fled since Isis seized the area in the summer of 2014.

Meanwhile, the Iraqi army has also moved into villages to the south of the city, where local tribes had ousted Isis on their own.

Early reports suggested the peshmerga advance from the east met relatively little resistance while the Iraqi army and Shia militias advancing from the south faced tougher opposition and more difficult terrain.
Battle for Mosul: Isis city under attack from Iraqi and Kurdish forces as it happened
The Iraqi army and Kurdish peshmerga fighters are converging on Iraqs second-largest city, which has been in the hands of Islamic State since 2014
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Under a US-brokered agreement negotiated in the run-up to the offensive, thepeshmerga and Shia militias such as the Iranian backed Hashd al-Shaabi are supposed to stop short of entering Mosul itself, which is mostly Sunni, allowing the Iraqi armys counter-terrorism force, federal police and local tribal fighters to conduct the house-to-house fighting in the city, with the aim of minimising sectarian conflict in the aftermath of the battle against Isis.

US, British and French special forces are playing a supporting role in the offensive, some giving coordinates on enemy targets for airstrikes. The US has a total 5,000 troops in Iraq, many serving as advisors to the 12 Iraqi brigades that have been specifically trained for the battle of Mosul. An ABC correspondent covering the peshmerga advance reported that US troops from the 101st Airborne Division were operating openly with the Kurds.

Early indications are that Iraqi forces met their objections and are ahead of schedule on this first day. Peter Cook, the Pentagon spokesman, said.

He said Isis has an estimated force of between three and five thousand inside the city, which has a population of about a million.

They have had two years to dig in and to plan IEDs [improvised explosive devices- booby-traps], Cook said. This is an enemy with a capacity to make life difficult.

He added that when Iraqi forces identify an Isis stronghold, they may pass on the coordinates to US forward air controllers serving behind the front line. Any subsequent air strike would have to be approved by the US command and the Iraqi authorities.

There are Americans on the outskirts of the city, but Iraqis are in the lead, and the Americans are operating behind the forward line, Cook said.