Near Mosul, Iraq (CNN) The battle to recapture Mosul from ISIS could take two months, a Peshmerga military commander told CNN on Tuesday, the second day of the long-awaited offensive to liberate Iraq's second city.

Sirwan Barzani, a brigadier general, said it would likely take two weeks for advancing forces to enter the city. Iraq's leaders have said that only Iraqi government troops and national police officers will be allowed to do so amid fears of sectarian retribution, he said.

A 94,000-member coalition of Iraqi security forces, Kurdish Peshmerga allies and thousands of irregulars from various minorities are involved in the operation to free Mosul from more than two years of ISIS rule.

Latest developments

• Iraqi forces begin operation to clear ISIS from the largely Christian town of Qaraqosh, southeast of Mosul.

• Moving in teams of 12 to 16 troops, US special operations forces are alongside Iraqi and Kurdish Peshmerga forces as they're heading toward Mosul from the south and east, US officials said. The US teams are advising and coordinating with those forces on how to maneuver on the ground, and how to coordinate artillery and air attacks, officials said.

• Turkish Prime Minister Binali Yildirim walks back an earlier claim that Turkish warplanes took part in air operations in Mosul with the US-led coalition.

• US President Barack Obama says Iraq's fight to take Mosul from ISIS will be successful but difficult. "(ISIS) will be defeated in Mosul, and that will be another step in their ultimate destruction," he told reporters in Washington

• One Iraqi soldier was killed while repelling an ISIS car bomb attack on government troops about 30 miles southeast of Mosul. Ten ISIS fighters were killed.

Tanks from the 9th Iraqi armored division advance on Mosul.

Progress east and south of Mosul

Iraqi security forces reported progress to the east and south of Mosul on their approach to the city.

An armored division began an operation to clear ISIS from Qaraqosh , a largely Christian, now mostly vacant town, which had about 50,000 residents before ISIS captured it two years ago.

Iraqi forces hold a position on Monday in the area of al-Shurah, some 45 kilometers south of Mosul.

Farther south, residents of villages near Qayyara have been fleeing their homes as Iraqi forces try to clear the area of ISIS.

A CNN team encountered about 200 people, including dozens of children, who had left their homes near the Tigris River, fearful of an ISIS counterattack.

Families, clustered behind a sand berm, had been trapped in their village since ISIS occupied it more than two years ago.

Tunnels uncovered

Iraqi media reported that in the historic village of Nimrod, once an Assyrian city dating from 1250 B.C., ISIS had destroyed precious archaeological remains.

Attacking forces have uncovered tunnels used by ISIS. One Kurdish television crew found a tunnel, whose entrance was inside a mosque, which had beds, food and a list of people who lived there.

Peshmerga forces are seen at Naveran front during an operation in Nineveh, Iraq on Tuesday.

The coalition vastly outnumbers its opponents, but ISIS, which has known the push was coming, has constructed elaborate defenses, including the network of tunnels. Coalition forces will also likely face suicide bombs, car bombs and booby traps.

Up to 5,000 ISIS fighters are in Mosul, a US military official said. ISIS' supporters put the number at 7,000.

Morale high

Advancing forces have encountered scattered resistance from ISIS fighters on their approach to Mosul. On Tuesday, one Iraqi soldier was killed and two were wounded while repelling suicide car bomb attacks southeast of the city. But morale remained high among the troops.

"Next stop, Mosul," said Sgt. Muhanned Hameed, a technician in the 9th Iraqi armored division, flashing a victory sign in front of his convoy.

"Next stop, Mosul," says Sgt. Muhanned Hameed, a technician in the 9th Iraqi armored division.

Others were more reflective. One mechanic in the division said that while he was excited about reaching Mosul, "God help those who had to flee."

"It always hurts to see the children's clothing on the ground, thrown around. Sometimes we try to pick it up, put it away. I keep imagining, what if it was my house?"

Progress was swifter than expected on the operation's first day, as forces advanced on the oil-rich northern city with support from roughly 90 coalition and Iraqi planes, retaking more than 75 square miles and wresting nine villages from ISIS control.

JUST WATCHED Dramatic moments from the battle for Mosul Replay More Videos ... MUST WATCH Dramatic moments from the battle for Mosul 01:16

Forces east of Mosul also secured control over a significant stretch of the Irbil-Mosul road, a key strategic route, the General Command of Peshmerga Forces of Kurdistan Region said, while Iraq's military declared that it had inflicted "heavy losses of life and equipment" on ISIS to the southeast.

It appeared US troops were in the first column of Peshmerga to cross into ISIS-held territory at dawn Monday. The troops wore clothes consistent with US forces -- including one who wore a US flag patch on his arm -- and were driving vehicles distinctive to the US military.

The United States, which lent advisers and air support, had earmarked about 500 of its nearly 5,000 service members in the country for the mission. Most are working on logistics, although there are also special operations forces among that number.

The United States still believes ISIS may try to use rudimentary mustard agent as a chemical weapon in the campaign's final stages. There are reports of ISIS setting fires to oil and tire pits to try to use the smoke to obscure their locations from aircraft targeting them.

Did Turkish planes take part?

Turkish Prime Minister Binali Yildirim walked back a claim he made earlier in the day that the Turkish air force had taken part in air operations in Mosul with the US-led coalition.

Initially, Yildirim told a meeting of the ruling AKP in parliament in Ankara that "our forces took part in air operations together with coalition forces," and that "this is an answer to those who said 'Turkey has no place in Mosul.'"

24 hours in: What has been achieved At least 9 villages liberated on first day

75 sq miles (200 sq km) of territory gained by coalition forces

Pentagon spokesman: Iraqi forces have "met their objectives" so far and are "ahead of schedule"

Also warns: Offensive "will be a difficult campaign that could take some time"

Later, when a reporter asked if Turkish planes had participated, Yildirim said: "I do not know the details of the operation," the state-run Anadolu news agency reported.

Ankara has been embroiled in a spat with Baghdad over the presence of Turkish soldiers in Nineveh province, northeast of Mosul, which has threatened to complicate the coordination between the two key US allies in the fight against ISIS.

Iraq's government objects to the presence of the troops, which it says are there without its permission, while Turkey is concerned the operation will fuel sectarian violence in the city. The soldiers are there to train Kurdish and Arab fighters as part of an agreement between Ankara and the semi-autonomous Kurdish Regional Government in northern Iraq.

JUST WATCHED ISIS fires shots at CNN reporter Replay More Videos ... MUST WATCH ISIS fires shots at CNN reporter 03:32

Why Mosul is so significant

Photos: Mosul: Iraqi-led forces push into key city Members of the Iraqi federal police wave the country's flag as they celebrate in the Old City of Mosul on July 9, 2017. Iraq declared victory against ISIS forces in Mosul after a grueling monthslong campaign. The battle to reclaim Mosul, the last major ISIS stronghold in Iraq, has been underway since fall 2016. Hide Caption 1 of 73 Photos: Mosul: Iraqi-led forces push into key city This injured girl was found by Iraqi forces as they advanced against ISIS militants in the Old City of Mosul on Monday, July 3. She was carried away for medical assistance. Hide Caption 2 of 73 Photos: Mosul: Iraqi-led forces push into key city A suspected ISIS fighter is held in a basement while Iraqi forces continue to push for control of the Old City of Mosul on Monday, July 3. Hide Caption 3 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi Special Forces soldier exchanges fire with ISIS militants in the Old City on Friday, June 30. Hide Caption 4 of 73 Photos: Mosul: Iraqi-led forces push into key city A bomb explodes near the al-Nuri mosque complex on Thursday, June 29. Iraq's military has seized the remains of the Great Mosque of al-Nuri. Iraq and the United States have accused ISIS of blowing up the historic mosque. Hide Caption 5 of 73 Photos: Mosul: Iraqi-led forces push into key city Members of the Iraqi Federal Police hold a position as US-led coalition forces advance through the Old City on Wednesday, June 28. Hide Caption 6 of 73 Photos: Mosul: Iraqi-led forces push into key city The remnants of Mosul's ancient leaning minaret are seen in the Old City on Sunday, June 25. ISIS' claim that US warplanes were responsible for the destruction of the minaret is "1,000% false," US officials told CNN. Hide Caption 7 of 73 Photos: Mosul: Iraqi-led forces push into key city Two boys comfort each other after their home collapsed during fighting between Iraqi forces and militants in Mosul on Saturday, June 24. The boys, who are cousins, said some of their relatives were still under the rubble. Hide Caption 8 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi soldier helps transport a girl as residents flee their homes west of Mosul on Friday, May 26. Hide Caption 9 of 73 Photos: Mosul: Iraqi-led forces push into key city Displaced Iraqis make their way through rubble after evacuating their homes in a neighborhood of west Mosul on Wednesday, May 17. Hide Caption 10 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi man tries to extinguish a burning car during fighting in Mosul's western Rifai neighborhood on Tuesday, May 16. Hide Caption 11 of 73 Photos: Mosul: Iraqi-led forces push into key city A member of the Iraqi counterterrorism service secures a building as troops push toward Mosul's Al-Oraibi western district on Sunday, May 14. Hide Caption 12 of 73 Photos: Mosul: Iraqi-led forces push into key city A smoke cloud rises on the front line as the Iraqi Emergency Response Division advances in west Mosul on Saturday, May 6. Hide Caption 13 of 73 Photos: Mosul: Iraqi-led forces push into key city A wounded man is transported in western Mosul on Friday, April 21. Hide Caption 14 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi federal policeman smokes during a break from battle on Wednesday, April 12. Hide Caption 15 of 73 Photos: Mosul: Iraqi-led forces push into key city A member of Iraq's security forces stands guard in eastern Mosul as smoke rises from the ISIS-controlled western section of the city on Friday, April 7. Hide Caption 16 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqis visit a bath house on the southern outskirts of Mosul on Wednesday, April 5. Hide Caption 17 of 73 Photos: Mosul: Iraqi-led forces push into key city Flames billow from an explosion in Mosul during a clash between Iraqi forces and ISIS fighters on Sunday, March 5. Hide Caption 18 of 73 Photos: Mosul: Iraqi-led forces push into key city Families are forced to evacuate as Iraqi forces advance in western Mosul on Thursday, March 2. The number of internally displaced people has surged as the offensive effort has intensified. Hide Caption 19 of 73 Photos: Mosul: Iraqi-led forces push into key city Mosul residents cross a damaged bridge in the al-Sukkar neighborhood on Saturday, January 21. Hide Caption 20 of 73 Photos: Mosul: Iraqi-led forces push into key city French President Francois Hollande and French Defense Minister Jean-Yves Le Drian, right, view territory held by ISIS during a visit to a military outpost near Mosul on Monday, January 2. Hide Caption 21 of 73 Photos: Mosul: Iraqi-led forces push into key city A young girl takes part in a Christmas Day Mass at a church in the predominantly Christian town of Qaraqosh. The area's churches were heavily damaged by ISIS militants before the town was freed by Iraqi forces during the Mosul offensive. Hide Caption 22 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi Shiite fighters ride through a desert area near the village of Al-Boutha al-Sharqiyah, west of Mosul, on Friday, December 2. Hide Caption 23 of 73 Photos: Mosul: Iraqi-led forces push into key city Internally displaced Iraqis who fled the fighting in Mosul watch as a civilian drone films them at the al-Khazir camp on Thursday, December 1. Hide Caption 24 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi soldier searches a home for ISIS militants after Iraqi forces retook the village of Al-Qasr on Wednesday, November 30. Hide Caption 25 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi soldiers transport a comrade who was injured during a battle near the village of Haj Ali on Tuesday, November 29. Hide Caption 26 of 73 Photos: Mosul: Iraqi-led forces push into key city A man mourns during the funeral of four Iraqi paramilitary fighters who were killed in battles in the town of Tal Afar. Hide Caption 27 of 73 Photos: Mosul: Iraqi-led forces push into key city Displaced civilians return to the village of Tall Abtah on Friday, November 25, after Iraqi forces retook the village from ISIS. Hide Caption 28 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi civilians sit on the ground in Mosul on November 24. An Iraqi officer addressed the group, demanding to know the whereabouts of alleged ISIS militants who opened fire on troops a few days earlier. Hide Caption 29 of 73 Photos: Mosul: Iraqi-led forces push into key city An injured baby receives treatment at a field hospital in Mosul on November 15. Hide Caption 30 of 73 Photos: Mosul: Iraqi-led forces push into key city A woman cries Sunday, November 13, after seeing the St. Addai church that was damaged by ISIS fighters during their occupation of the Keramlis village. Hide Caption 31 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi special forces soldier prays next to a Humvee before troops pushed toward Mosul's Karkukli neighborhood on November 13. Hide Caption 32 of 73 Photos: Mosul: Iraqi-led forces push into key city A Kurdish Peshmerga fighter holds part of a defused bomb planted by ISIS militants in Bashiqa, Iraq, on Friday, November 11. Hide Caption 33 of 73 Photos: Mosul: Iraqi-led forces push into key city A member of Iraq's special forces guards two suspected ISIS fighters found hiding in a house in Mosul on November 11. Hide Caption 34 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi woman displaced by war holds her cat near a checkpoint in the Iraqi village of Shaqouli, east of Mosul, on November 10. Hide Caption 35 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi troops watch a broadcast of Donald Trump's acceptance speech in a house in Arbid, on the outskirts of Mosul, on Wednesday, November 9. Iraqi Prime Minister Haider al-Abadi congratulated Trump on his win and said he hoped for continued support in the war on ISIS. Hide Caption 36 of 73 Photos: Mosul: Iraqi-led forces push into key city US Marines install equipment at a coalition base in Qayyara on November 9. Hide Caption 37 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi forces member investigates a mass grave that was discovered after coalition forces recaptured the area of Hamam al-Alil on Monday, November 7. Hide Caption 38 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi children witness a man being interrogated by a member of the Iraqi army at a base next to the Al-Intissar neighborhood of Mosul on November 7. Hide Caption 39 of 73 Photos: Mosul: Iraqi-led forces push into key city A civilian man who fled the fighting trims his beard after reaching an Iraqi army position in Mosul on November 7. Hide Caption 40 of 73 Photos: Mosul: Iraqi-led forces push into key city Children play in debris created by an airstrike in Qayyara on Sunday, November 6. Hide Caption 41 of 73 Photos: Mosul: Iraqi-led forces push into key city Female members of the Freedom Party of Kurdistan sing as they hold a position near Bashiqa on November 6. Hide Caption 42 of 73 Photos: Mosul: Iraqi-led forces push into key city A baby is passed through a fence back to his mother at a refugee camp in the Khazir region on Saturday, November 5. Hide Caption 43 of 73 Photos: Mosul: Iraqi-led forces push into key city People line up to receive food at a refugee camp in the Khazir region on November 5. Thousands are taking refuge in camps set up for internally displaced people. Hide Caption 44 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi soldiers pass near a bridge destroyed in an airstrike in Qayyara on November 5. Hide Caption 45 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi soldiers patrol an alley on the outskirts of Mosul on Friday, November 4. Hide Caption 46 of 73 Photos: Mosul: Iraqi-led forces push into key city A suspected member of ISIS is detained at a checkpoint near Bartella, Iraq, on November 4. Hide Caption 47 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi families pack into a truck to be moved to camps on Thursday, November 3. Hide Caption 48 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi special forces soldier searches for the location of an ISIS sniper in Gogjali on November 1. Hide Caption 49 of 73 Photos: Mosul: Iraqi-led forces push into key city A man fleeing the village of Bazwaya carries a white flag as he arrives at a checkpoint on November 1. Hide Caption 50 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi soldier receives treatment after being injured during clashes with ISIS fighters near Bazwaya on October 31. Hide Caption 51 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi soldier navigates through a shattered windshield as coalition forces advance on Bazwaya on October 31. Hide Caption 52 of 73 Photos: Mosul: Iraqi-led forces push into key city Archbishop Yohanna Petros Mouche, center, performs Mass in the liberated town of Qaraqosh on Sunday, October 30. Hide Caption 53 of 73 Photos: Mosul: Iraqi-led forces push into key city Children play in a camp for internally displaced people near Kirkuk, Iraq, on October 30. More than 600 families from Tel Afar, a town west of Mosul, have been living in the camp since ISIS took control of the area in 2014. Hide Caption 54 of 73 Photos: Mosul: Iraqi-led forces push into key city Displaced families are seen on the road near Qayyara on Saturday, October 29. Hide Caption 55 of 73 Photos: Mosul: Iraqi-led forces push into key city U.S. military personnel take cover in a bunker after a mortar alarm was sounded at a coalition air base in Qayyara on Friday, October 28. Hide Caption 56 of 73 Photos: Mosul: Iraqi-led forces push into key city Women and children grieve over the grave of a family member at a Qayyara cemetery damaged by ISIS on October 27. Hide Caption 57 of 73 Photos: Mosul: Iraqi-led forces push into key city Residents of Qayyara wait for distribution of food and water rations on October 26. Local water sources have been contaminated by the burning oil and sulfur. Hide Caption 58 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraq's counterterrorism forces advance toward ISIS positions in Tob Zawa on October 25. Hide Caption 59 of 73 Photos: Mosul: Iraqi-led forces push into key city Soldiers give first aid to an injured boy in Tob Zawa on October 25. Hide Caption 60 of 73 Photos: Mosul: Iraqi-led forces push into key city Kurdish Peshmerga forces take positions as they start to move toward the Imam Reza and Tizxirab villages of the Bashiqa district on Sunday, October 23. Hide Caption 61 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi forces distribute fruit in the village of al-Khuwayn, south of Mosul, after recapturing it from ISIS on October 23. Hide Caption 62 of 73 Photos: Mosul: Iraqi-led forces push into key city Kurdish security forces detain a suspected member of ISIS in the eastern suburbs of Kirkuk on Saturday, October 22. Hide Caption 63 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi forces member helps a man push a car as they arrive at a refugee camp in Qayyara on October 22. Hide Caption 64 of 73 Photos: Mosul: Iraqi-led forces push into key city Spent bullet cartridges litter the street around the Jihad Hotel, where ISIS militants battled Iraqi security forces in Kirkuk on Friday, October 21. Hide Caption 65 of 73 Photos: Mosul: Iraqi-led forces push into key city Gen. Abdel Ghani al-Asadi, who leads Iraq's counterterrorism forces, sits in Bartella on October 21 after the town was reclaimed. Hide Caption 66 of 73 Photos: Mosul: Iraqi-led forces push into key city Peshmerga fighters look over a village during an assault near Bashiqa on Thursday, October 20. Hide Caption 67 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi forces head toward the front lines near Qayyara on Tuesday, October 18. Hide Caption 68 of 73 Photos: Mosul: Iraqi-led forces push into key city A Peshmerga fighter peers up from an underground tunnel in the liberated town of Badana on October 18. ISIS fighters have built tunnels below residential streets to escape from airstrikes. Hide Caption 69 of 73 Photos: Mosul: Iraqi-led forces push into key city Kurdish security forces take up a position near ISIS-controlled villages on Monday, October 17. Hide Caption 70 of 73 Photos: Mosul: Iraqi-led forces push into key city Smoke rises from a suicide car bomb attack carried out by ISIS in the village of Bedene on October 17. Hide Caption 71 of 73 Photos: Mosul: Iraqi-led forces push into key city Members of the Iraqi coalition gather around a fire at Zardak mountain ahead of the offensive. Hide Caption 72 of 73 Photos: Mosul: Iraqi-led forces push into key city Peshmerga forces deploy in the dark near the village of Wardak early on October 17. Hide Caption 73 of 73

Since Mosul's capture by ISIS fighters in June 2014, Mosul has been a vital stronghold for ISIS.

The largest city under ISIS control in Iraq and Syria, it was the city from which the group first declared the establishment of its so-called caliphate.

Since then, ISIS has gradually lost its other Iraqi cities -- Ramadi, Tikrit and Falluja -- to government forces. About 1 million people are estimated to remain in Mosul, once a cosmopolitan trade hub of 2 million residents.