BAWIZA, Iraq (Reuters) - Iraqi soldiers fighting just north of Mosul, within sight of city neighborhoods, said on Sunday they were ready to tighten the noose around Islamic State militants waging a brutal defense of their Iraqi stronghold.

Four weeks into the campaign to crush Islamic State in Mosul, the city is almost surrounded but the jihadists’ defenses have so far been breached only to the east, where they have battled elite troops for control of around a dozen districts.

The battle for Mosul, the biggest city held by the ultra-hardline Sunni Islamist group in Iraq and Syria, is the largest military operation in Iraq in a decade of turmoil unleashed by the 2003 U.S. invasion which toppled Saddam Hussein.

Iraq’s Shi’ite-led government, which has assembled a 100,000-strong coalition of troops, security forces, Kurdish peshmerga fighters and mainly Shi’ite militias, backed by U.S. air power, says it will mark the end of Islamic State in Iraq.

But it says the fight will be a long one.

An army special forces officer on the northern front line said his men aimed to target Hadba, the first neighborhood ahead of them within city limits. The district was visible from his position in the village of Bawiza.

Brigadier Ali Abdulla said Islamic State fighters had been pushed out of Bawiza and another village, Saada, although progress had been slowed by the presence of civilians he said were being used by the militants as human shields.

“Our approach (to Hadba) will be very slow and cautious so that we can reach the families and free them from Daesh’s (Islamic State’s) grip,” Abdulla said.

One man who escaped from Saada to Bawiza with his young son and daughter said they had to move from house to house and hide among sheep to avoid being caught by Islamic State fighters.

The timing of the decision to move on Hadba would depend on progress on other fronts, Abdulla said. Security forces are advancing to the south of Mosul, targeting the city’s airport on the west bank of the Tigris river.

Abdulla said Islamic State was using suicide car bombs, roadside bombs, snipers and long range mortars to try to hold back the army advance in the north - all tactics it has used to lethal effect on the eastern front as well.

Another officer, Captain Oqba Nafaa, said the militants were still fighting in Saada, using a network of tunnels to carry out surprise strikes on the attacking forces.

The urban warfare tactics were similar to those they have deployed to lethal effect in the east of the city against elite Counter Terrorism Service (CTS) forces and an armored division.

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In some districts, control has changed hands three or four times as the militants, using tunnels and exploiting the presence of civilians as cover, have launched night-time attacks and reversed military gains of the previous day.

One resident of al-Qadisiya al-Thaniya district, which the CTS entered on Friday, said the special forces later pulled back and Islamic State fighters returned.

“They came back to us again, and this is what we feared. At night there were fierce clashes and we heard powerful explosions,” she told Reuters.

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A military statement later said that CTS forces had cleared all militants from two districts of eastern Mosul, Arbajiya and Karkukli, and were still clearing three others.

TROOPS TAKE NIMRUD

About 30 km (20 miles) south of Mosul, troops recaptured the 3,000-year-old Assyrian city of Nimrud which was overrun by Islamic State militants two years ago, a military source said.

Nimrud, once the capital of an empire stretching across the ancient Middle East, is one of several historic sites looted and ransacked by the militants, who deem the country’s pre-Islamic religious heritage idolatrous.

Iraq’s deputy culture minister, Qais Hussain Rasheed, said that recapturing the remains of Iraq’s rich heritage from the jihadists represented a triumph for the world.

Islamic State still controls other Assyrian landmarks including the ruins of Nineveh and Khorsabad, as well as the 2,000-year-old desert city of Hatra.

“Liberation of ancient Iraqi archaeological sites from the control of forces of dark and evil is a victory not only to Iraqis but for all humanity,” Rasheed, deputy minister for tourism and antiquities at the culture ministry, told Reuters.

The scale of the damage inflicted on the sites is not completely clear, but Iraqi officials say many buildings have been totally destroyed.

More than 54,000 people have been forced to flee their homes so far in the Mosul campaign.

The Norwegian Refugee Council said on Sunday tens of thousands of people “lack access to water, food, electricity and basic health services” in areas recaptured by the army in Mosul and surrounding towns and villages.

Ultimately, 700,000 people were likely to need shelter, food, water or medical support.

In the north of the country, Iraqi Kurdish fighters battling Islamic State unlawfully destroyed Arab homes in scores of towns and villages in what may amount to a war crime, the U.S.-based rights group Human Rights Watch said on Sunday.