* 7,500 Kurdish and Yazidi fighters backed by coalition firepower
* Sinjar lies strategically on road linking Mosul and Raqqa
* Islamic State attack last year triggered U.S.-led air strikes (Adds Kurdish predictions Sinjar will be captured soon)
By Isabel Coles
NEAR SINJAR TOWN, Iraq, Nov 12 (Reuters) - Kurdish forces who have launched an offensive to retake Sinjar from Islamic State militants expect to enter and clear the northern Iraqi town soon, the Kurdistan regional security council said on Thursday.
More than 150 square km (58 square miles) have been seized from the ultrahardline Sunni group and dozens of bodies of its fighters were left behind in a retreat from parts of Sinjar, it added.
Reuters could not independently confirm this account but Kurdish commanders near the frontline seemed confident and morale among fighters was high.
Backed by U.S.-led coalition air strikes, Kurdish peshmerga fighters reached Sinjar from the east and west, the council said.
The Kurds launched the operation in the early morning designed to cordon off Sinjar, take control of strategic routes and establish a buffer zone to protect the town from artillery.
A victory in Sinjar could give the Kurds, government forces and Shi'ite militias critical momentum in efforts to defeat Islamic State, which controls large areas of Iraq and Syria and has affiliates in Libya and Egypt.
The group, made up of Iraqis and other Arabs as well as foreign fighters, poses the biggest security threat to OPEC oil producer Iraq since a U.S.-led invasion toppled Saddam Hussein in 2003.
So far the Kurds have captured several villages and taken up positions along Highway 47, a supply route between Raqqa in Syria and the Iraqi city of Mosul, the main Islamic State bastions.
"The ground assault began in the early morning hours of Nov. 12, when peshmerga units successfully established blocking positions along Highway 47 and began clearing Sinjar," said the coalition in a statement.
"The peshmerga will continue operations to re-establish government control over key portions of the areas."
Islamic State, suspected by Western intelligence officials of playing a role in the crash of a Russian passenger plane in Egypt two weeks ago, overran Sinjar more than a year ago.
Islamic State's killing and enslaving of thousands of its Yazidi residents focused international attention on the group's violent campaign to impose its radical ideology and prompted Washington to launch its air offensive.
The U.S. expectation is that it would take two to four days to secure Sinjar and another week to finalise clearing operations, a U.S. military official said, speaking on condition of anonymity.
U.S. military advisers are with Kurdish commanders near Sinjar mountain but are positioned well back from the fighting, a U.S. military spokesman said.
U.S. Army Colonel Steve Warren told Reuters some U.S. advisers were also on Sinjar mountain working with the Kurdish peshmerga forces to advise and assist with the development of targets for air strikes.
The U.S. military estimated that 60 to 70 Islamic State fighters had been killed in U.S.-led coalition air strikes so far on Thursday, said Warren, a Baghdad-based spokesman for the U.S.-led coalition effort against Islamic State.
Islamic State uses Highway 47 to transport weapons, fighters and illicit commodities to fund its operations, said the coalition, which conducted more than 250 air strikes in the past month across northern Iraq.
Russia's recent interventions - air strikes against opponents of President Bashar al-Assad in Syria and intelligence sharing with Baghdad - have raised concerns in Washington that its former Cold War foe is gaining influence in the Middle East.
U.S.-led coalition air strikes pounded Islamic State-held areas in the town overnight, as around 7,500 Kurdish special forces, peshmerga and Yazidi fighters descended from the Sinjar mountain towards the front line in a military convoy.
"It is going according to plan. We are optimistic and we consider today like a celebration," said Sinjar district mayor Mahma Xelil.
Kurdish forces and the U.S. military said the number of Islamic State fighters in the town had increased to nearly 600 after reinforcements arrived in the run-up to the offensive.
The offensive is being overseen by Kurdistan regional president Massoud Barzani, who is also head of the Kurdistan Democratic Party (KDP), which other groups in the area accuse of seeking to monopolise power.
Many Yazidis lost faith in the KDP when its forces failed to protect them from Islamic State militants, who consider them devil worshippers, when the group attacked Sinjar in August 2014, systematically slaughtering, enslaving and raping thousands of Yazidis.
A Syrian affiliate of the Kurdistan Workers' Party (PKK) came to the rescue, evacuating thousands of Yazidis stranded on Sinjar mountain and establishing a permanent base there.
Near the front lines on Thursday, a Kurdish officer stood behind a wall of sandbags. Sinjar, about 300 metres (1,000 feet)away, could be seen through a gap in a rampart.
Kurdish officers said an Islamic State sniper had taken up position in the town. Coordinates were passed to a joint operations room and within five minutes the position was bombed.
Islamic State militants could be heard communicating in Arabic and Turkmen in intercepted walkie-talkie chatter.
"Where are you," asked one. "Praise be to God," said another. One fighter noted that a car used by his comrades had been destroyed.
Loqman Ibrahim, head of the eight battalion, made up of Yazidis and under peshmerga command, said he heard militants urging each other to fight to the death and that an order was given not to withdraw.
Most Yazidis have been displaced to camps in the Kurdistan region; several thousand remain in Islamic State captivity.
LAND AND HONOUR
For Yazidi forces taking part, the battle is very much about retribution.
Hussein Derbo, the head of a peshmerga battalion made up of 440 Yazidis, said the men under his command could have migrated to Europe but chose to stay and fight.
"It is our land and our honour. They (Islamic State) stole our dignity. We want to get it back," he told Reuters in a village on the northern outskirts of Sinjar town.
Derbo's brother, Farman, echoed the sentiment, saying he hoped the militants would not retreat so the Yazidis could kill them all.
The forces, many wearing the thick moustache typical of Yazidis and carrying light weapons, had gathered at a staging position overnight.
They travelled in a peshmerga convoy comprised of Humvees on flatbed trucks, heavy artillery, and fighters waving Kurdish flags, flashing peace signs and brandishing their rifles.
Hundreds of vehicles wound slowly downhill along the same road Yazidis had fled up last summer seeking safety from Islamic State. Abandoned cars and blood-stained clothing were reminders of those chaotic scenes.
Around dawn, the fighters piled into their vehicles and headed to the front.
Authorising the first strikes against Islamic State in August 2014, U.S. President Barack Obama cited a duty to prevent a genocide of Yazidis by the radical Islamists.
In December 2014, Kurdish forces drove Islamic State from north of Sinjar mountain, a craggy strip about 60 km (40 miles) long, but Islamic State maintained control of the southern side where the town is located.
(Writing by Michael Georgy; Editing by James Dalgleish)
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