SOUTH OF MOSUL/BAGHDAD, Iraq (Reuters) - U.S.-backed Iraqi forces battling Islamic State fighters have fought their way close to Mosul’s airport on the second day of a ground offensive on the jihadists’ remaining stronghold in the western side of the city, military statements said on Monday.

Members of the Iraqi rapid response forces fire a missile toward Islamic State militants during a battle in the south of Mosul, Iraq February 19, 2017. REUTERS/Zohra Bensemra

Federal police and elite interior ministry units known as Rapid Response are leading the charge toward the airport on the southern outskirts of Mosul and plan to turn it into a close support base for the push into western Mosul, commanders have said.

They dislodged Islamic State fighters from the hilltop village of Albu Saif which overlooks the airport, reaching its “vicinity,” an Iraqi military statement said.

The militants are essentially under siege in western Mosul, along with an estimated 750,000 civilians, after they were forced out of the eastern part of the city in the first phase of the campaign that ended last month, after 100 days of fighting.

“They are striking and engaging our forces and pulling back towards Mosul,” Major Mortada Ali Abd of the Rapid Response units told a Reuters correspondent south of Mosul. “God willing Albu Saif will be fully liberated today.”

Elite Counter-Terrorism Service units headed to frontlines around the western side of Mosul, a city divided in two by the Tigris River.

Helicopters were seen strafing the Albu Saif hill during the day to clear it of snipers, while machinegun fire and rocket propelled grenades could be heard. The advancing forces also disabled a car bomb, used by militants to obstruct attacking forces.

The Iraqi forces have been advancing so far in sparsely populated areas and there were no families seen escaping. The fighting will get tougher as they get nearer to the city itself and the risk greater for civilians.

Up to 400,000 civilians could be displaced by the offensive as residents of western Mosul suffer food and fuel shortages and markets are closed, United Nations Humanitarian Coordinator for Iraq Lise Grande told Reuters on Saturday.

Commanders expect the battle to be more difficult than in the east of the city, which Iraqi forces took control of last month after three months of fighting. Tanks and armored vehicles cannot pass through its narrow alleyways.

The militants have developed a network of passageways and tunnels to enable them to hide and fight among civilians, disappear after hit-and-run operations and track government troop movements, according to residents.

Western Mosul contains the old city center, with its ancient souks, government administrative buildings, and the mosque from which Islamic State leader Abu Bakr al-Baghdadi declared his self-styled caliphate over parts of Syria and Iraq in 2014.

The city is the largest urban center captured by Islamic State in both countries.

The U.S. commander in Iraq, Army Lieutenant General Stephen Townsend, told a news conference in Baghdad on Monday he had been putting U.S. military advisers closer to front lines in Mosul.

“We adjusted our posture during the east Mosul fight and we embedded advisers a bit further down into the formation,” he said, speaking during an unannounced visit of Defense Secretary Jim Mattis to Baghdad.

Townsend has said he believes U.S.-backed forces will recapture both of Islamic State’s major strongholds - Mosul and the city of Raqqa in Syria - within the next six months.

Islamic State was thought to have up to 6,000 fighters in Mosul when the government’s offensive started in mid-October. Of those, more than 1,000 have been killed, according to Iraqi estimates.

The remainder now face a 100,000-strong force made up of Iraqi armed forces, including elite paratroopers and police, Kurdish forces and Iranian-trained Shi’ite paramilitary groups.

The westward road that links the city to Syria was cut in November by the Shi’ite paramilitary known as Popular Mobilization forces. The militants are in charge of the road that links Mosul to Tal Afar, a town they control 60 km (40 miles) to the west.

CIVILIAN LIVES

Coalition aircraft and artillery have continued to bombard targets in the west during the break that followed the taking of eastern Mosul.

The United States, which has deployed more than 5,000 troops in the fighting, leads an international coalition providing air and ground support to the Iraqi and Kurdish forces.

Mattis told reporters before arriving in Baghdad the U.S. military was not in Iraq to seize the country’s oil, distancing himself from remarks by President Donald Trump.

A U.S. serviceman died on Monday in a non-combat related incident outside the Iraqi city of Ramadi, west of Baghdad, the U.S.-led coalition said, giving no further details.

Islamic State imposed a radical version of Islam in Mosul, banning cigarettes, televisions and radios, and forcing men to grow beards and women to cover from head to toe. Citizens who failed to comply risked death.

Capturing Mosul would effectively end the Sunni group’s ambitions for territorial rule in Iraq. The militants are expected to continue to wage an insurgency, however, carrying out suicide bombings and inspiring lone-wolf actions abroad.

About 160,000 civilians have been displaced since the start of the offensive in October, U.N. officials say. Medical and humanitarian agencies estimate the total number of dead and wounded - both civilian and military - at several thousand.

“This is the grim choice for children in western Mosul right now: bombs, crossfire and hunger if they stay – or execution and snipers if they try to run,” Save the Children said, adding children make up about half the population trapped in the city.

The involvement of many local and foreign players with diverging interests in the war heightens the risk that they could clash between themselves after Islamic State is defeated.

Influential Shi’ite cleric Moqtada al-Sadr, who is openly hostile to Washington’s policies in the Middle East, on Monday said U.S. troops should leave as soon as Mosul is captured.

Mattis declined to address Sadr’s remarks directly, describing them as an internal political matter, but he said he was reassured after his talks in Baghdad that Iraq’s leaders recognized the value of its relationship with the United States.

“I imagine we’ll be in this fight for a while and we’ll stand by each other,” he said.