BARTELLA, Iraq -- Iraqi special forces paused their advance in an eastern district of Mosul on Wednesday to clear a neighborhood of any remaining Islamic State of Iraq and Syria (ISIS), as forces further to the south of the city took four small villages, military officials said.

In Mosul’s easternmost Gogjali, special forces could be seen going house to house while sappers searched the road for explosives and booby traps left behind by the jihadis driven out a day earlier.

Gen. Abdul-Ghani al-Asadi, the top counter-terrorism forces commander, told reporters a curfew had been imposed in the neighborhood while gains there were being consolidated.

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“We fear that Daesh militants could attack our forces or the town with mortars,” he said, using the Arabic acronym for ISIS. “So for the safety of the families we ask them to stay inside their houses.” He spoke in the town of Bartella, some 15 kilometers behind the front lines.

Brig. Gen. Haider Fadhil said that no advances were planned while high humidity and clouds obscured the view of aircraft and drones - a key component to the operations provided by a U.S.-led air campaign.

The guns were largely silent in Gogjali, which is inside Mosul’s city limits but just outside more urban districts, although sporadic rifle cracks could be heard as well as some army artillery fire on ISIS positions. Fadhil said special forces had detained three suspected ISIS militants in the area.

The pause came a day after Iraqi troops set foot in the city for the first time in more than two years, gearing up for urban warfare expected to take weeks, if not months.

In the next stage, troops will have to navigate streets likely lined with booby traps, fighting house-to-house while trying to avoid killing civilians, more than one million of whom are still in the city.

Further to the south, where progress has been much slower, Federal Police forces captured four small villages outside the Hamam al-Alil area, over 30 kilometers from Mosul, the army said. The largest of the four is Min Gar, some 10 km west of Hamam al-Alil, spokesman Brig. Gen. Yahya Rasool said of the Wednesday morning operation.

Mosul is the last major ISIS stronghold in Iraq, and driving the militant group from the city would be a major blow to its ambitions of creating a cross-border “caliphate” stretching into Syria. ISIS announced the project in Mosul in 2014, after it routed the much larger Iraqi military, which had been neglected and demoralized by corruption.

However, concern over the fate of civilians caught up in the fighting has been growing, after residents reported that ISIS militants were rounding up thousands of people to use as human shields and killing those with suspected links to the security forces.

According to one account given to The Associated Press, the fighters went door to door in villages south of Mosul, ordering hundreds of people at gunpoint to march north into the city, where urban fighting is expected to be heaviest and the presence of civilians will slow the army’s advance as it tries to avoid killing innocents.

In the latest international condemnation of ISIS, which has carried out mass killings of perceived opponents in the past and boasted about them in grisly photos and videos circulated online, the United Nations called on authorities to collect evidence of ISIS abuses of civilians for future use by tribunals.

The Norwegian Refugee Council warned that more than 1 million civilians trapped inside Mosul “are in grave danger” as Iraqi troops advance into the city.

The aid group, which works with refugees and internally displaced people, said that around 18,000 Iraqis have fled their homes since the start of the massive Mosul military operation over two weeks ago.

Its Iraq chief, Wolfgang Gressmann, said the agency’s aid workers were “bracing ... for the worst.”

“The lives of 1.2 million civilians are in grave danger, and the future of all of Iraq is now in the balance,” he said

Adama Dieng, special adviser to the U.N. Secretary-General Ban Ki-moon on the prevention of genocide, also expressed concern over “the increasing risk” of sectarian violence or revenge attacks during the Mosul campaign, especially where state-sanctioned Iraqi Shiite militias are approaching Sunni communities.

“Any kind of retaliatory violence against individuals on the basis of their membership of a specific group is unacceptable,” he said in a statement released Tuesday.

Political rhetoric on the issue has been heating up, after Turkish President Recep Tayyip Erdogan recently warned that Turkey would be closely monitoring Shiite militias’ behavior in northern Iraq and seeking to safeguard the rights of ethnic Turkmens there. Erdogan said the Iraqi Shiite militias could prompt a Turkish response if they “terrorize” the Iraqi-Turkmen town of Tal-Afar.

On Tuesday, Turkey’s defense minister said his country was making preparations for “all kinds of possibilities” as the Turkish military began deploying tanks and other vehicles to the border town of Silopi.

In a televised speech later that evening to praise the Mosul operation, Iraqi Prime Minister Haider al-Abadi downplayed an escalation. “We don’t want war with Turkey. We do not want confrontation with Turkey,” he said. But if one happens, “we are ready.”.