Iraqi military finds 100 decapitated skeletons east of Mosul

The Iraqi military says it has found some 100 decapitated bodies in a mass grave south of the ISIS-held city of Mosul.

The spokesman for the Joint Military Command, Brig.-Gen. Yahya Rasool, says the bodies were discovered Monday near the agricultural college in the town of Hamam al-Alil. Most were reduced to skeletons.

A forensics team from Baghdad will investigate the site on Tuesday. Rasool says the state of the bodies made it difficult to tell by their clothes if they were soldiers or civilians.

Earlier Monday, Kurdish Peshmerga forces stormed an ISIS-held town northeast of Mosul on Monday, trying to clear a pocket of militants outside the city while Iraqi troops wage a fierce urban war with the jihadists in its eastern neighbourhoods.

As the operation against Islamic State in Iraq and Syria's Iraqi stronghold entered its fourth week, fighters across the border launched an offensive in the Syrian half of the jihadist group's self-declared caliphate, targeting its base in the city of Raqqa.

An alliance of U.S.-backed Kurdish and Arab groups launched the campaign for Raqqa, where the group Islamic State in Iraq and Syria has been dug in for nearly three years, with an assault on territory about 50 kilometres to the north which they have dubbed Euphrates Anger.

• Mosul battle rages as ISIS bombings kill at least 20
• Iraqi forces move deeper into Mosul

The battle for Raqqa will be every bit as challenging as the one for Mosul, with both cities carrying huge strategic and symbolic value to the jihadists and their self-declared caliphate covering territory in both Syria and Iraq.

The Iraqi operation, involving a 100,000-strong alliance of troops, security forces, Kurdish Peshmerga and Shia militias, backed by U.S.-led airstrikes and a global consensus against the jihadis, has so far gained just a small foothold in Mosul.

The Raqqa campaign, launched amid a complex civil war in Syria which has divided world powers, is not co-ordinated with President Bashar al-Assad or the Syrian army. The Kurdish element of SDF groups fighting towards Raqqa also makes them an unlikely force to recapture the Arab city.

"It is difficult to put a time frame on the operation at present," a Syrian Kurdish source said. "The battle will not be easy."

2,000 forces enter Bashiqa

In Bashiqa, some 15 kilometres from Mosul, the first waves of a 2,000-strong Peshmerga force entered the town on foot and in armoured vehicles or Humvees.

Artillery earlier pounded the town, which lies on the Nineveh plains at the foot of a mountain.

"Our aim is to take control and clear out all the Islamic State militants," Lt.-Col. Safeen Rasoul told Reuters. "Our estimates are there are about 100 still left and 10 suicide cars."

ISIS fighters have sought to slow the offensive on their Mosul stronghold with waves of suicide car bomb attacks. Iraqi commanders say there have been 100 on the eastern front and 140 in the south.

A top Kurdish official told Reuters on Sunday the jihadists had also deployed drones strapped with explosives, long-range artillery shells filled with chlorine gas and mustard gas and trained snipers.

As a Peshmerga column moved into Bashiqa on Monday, a loud explosion rocked the convoy, and two large plumes of white smoke could be seen just 15 metres away. A Peshmerga officer said two suicide car bombs had tried to hit the advancing force.

'They are surrounded'

"They are surrounded If they want to surrender, OK. If they don't, they will be killed," said Lt.-Col. Qandeel Mahmoud, standing next to a Humvee, supported by a cane he said he has needed since he was wounded in the leg by two suicide car bombers four months ago.

Armed U.S. soldiers, part of a 5,000 strong force Washington says is advising and supporting the Iraqi offensive, were accompanying the Peshmerga in Bashiqa through streets lined by rows of damaged houses, some with entire floors collapsed.

Fighting was intense, and at one stage a convoy of 40 vehicles was held up by a single ISIS sniper.

In eastern districts of Mosul, which Iraqi special forces broke into last week, officers say jihadists melted into the population, ambushing and isolating troops in what the special forces spokesman called the world's "toughest urban warfare."

Mosul, the largest ISIS-controlled city in either Iraq or Syria, has been held by the group since its fighters drove the army out of northern Iraq in June 2014. The campaign to retake it is the most complex military operation in Iraq since the 2003 U.S. invasion which toppled Saddam Hussein.

Twin offensives on Raqqa and Mosul could bring to an end the self-styled caliphate declared by ISIS leader Abu Bakr al-Baghdadi from the pulpit of a Mosul mosque in 2014.

Baghdadi, whose whereabouts are unknown but who is believed to be in northern Iraq close to the Syrian border, has told his followers there can be no retreat in a "total war" with their enemies.

Militants lose ground outside Mosul

The militants in Mosul have been waging a fierce and brutal defence, although they have lost ground on all fronts outside the city itself.

To the south of Mosul, security forces said they had recaptured and secured the town of Hammam al-Alil from ISIS fighters, who they said had kept thousands of residents as human shields as well as marching many others alongside retreating militants towards Mosul as cover from airstrikes.

The United Nations has warned of a possible exodus of hundreds of thousands of refugees from a city which is still home to up to 1.5 million people. So far 34,000 have been displaced, the International Organization for Migration said.

Many of those still in Mosul feel trapped, including those in districts which the army entered last week.

"We still can't go out of our houses mortars are falling continuously on the quarter," a resident of the Quds neighbourhood on the eastern edge of the city told Reuters by telephone on Sunday.

Security forces on the southern front have continued their advance, reaching within four kilometres of Mosul's airport, on the southern edge of the city and on the western bank of the Tigris River which runs through its centre.

To the north, a military statement said the army's Sixteenth Infantry Division had also recaptured the village of Bawiza and entered another area, Sada, on the city's northern limits, further tightening the circle of forces around ISIS.

Shia militias known as Popular Mobilisation forces are also fighting to the west of Mosul to seal the routes to the ISIS-held town of Tal Afar and its territory in neighbouring Syria, to prevent any retreat or reinforcement.