The push into Nimrud was the most significant gain in several days for government forces, potentially opening up the area for teams to assess the damage done to the famed ruins just outside the town. Troops are converging from several fronts on Mosul, Iraq's second-largest city and the biggest urban area under IS control, as part of an offensive launched last month.
The special forces have advanced the farthest so far, and hold a handful of districts on the city's eastern edge, but their progress has slowed in the face of fierce resistance in dense urban neighborhoods full of civilians.
The operation's commander said troops took Nimrud, some 19 miles (30 kilometers) south of Mosul, after heavy fighting. It was unclear if they had liberated the nearby 13th-century B.C. archaeological site, which IS destroyed with explosives according to videos they released.
"The 9th division of the Iraqi army has liberated the town of Nimrud completely and raised the Iraqi flag over its buildings after the enemy suffered heavy casualties," Lt. Gen. Abdul-Amir Raheed Yar Allah said in a statement.
The late 1980s discovery of treasures in Nimrud's royal tombs was one of the 20th century's most significant archaeological finds. The government said militants, who captured the site in June 2014, destroyed it the following year using heavy military vehicles.
Video footage released by the jihadis at the time showed bearded men hammering, bulldozing and ultimately blowing up parts of the ancient Iraqi treasure, ripping down huge alabaster reliefs depicting Assyrian kings and deities. They claim the artefacts promote idolatry that violates their fundamentalist interpretation of Islamic law.
Col. John Dorrian, a spokesman for the U.S.-led forces operating the air campaign assisting the operation against IS, said few airstrikes were used near Nimrud, and the advancing Iraqi troops had moved in carefully.
"It's an important gain," he said, but warned that IS often leaves behind some combatants. "As Iraqi forces get closer to Mosul, everything becomes more difficult as they like to leave behind a few fighters to spoil the advance."
In Mosul itself, the special forces said they have cleared the Qadisiya and Zahra neighborhoods, and are planning to advance farther in the coming hours. Over the past week they have inched forward slowly, trying to avoid casualties among their troops and civilians as suicide bombers in armor-plated vehicles charge at them from hideouts in densely populated areas.
"The only weapons they have left are car bombs and explosives," said Iraqi special forces Maj. Gen. Sami al-Aridi as he radioed with commanders in the field. "There are so many civilian cars and any one of them could be a bomb," he said.
Troops were building berms and road blocks to prevent car bombs from breaching the front lines. Since last week's quick advance into Mosul proper, they have struggled to hold territory under heavy IS counterattacks.
Several suicide car bombers attacked the advancing special forces on Saturday, wounding around a dozen troops, three civilians, and killing a child, officers said. They spoke on condition of anonymity because they weren't authorized to brief reporters.
The Iraqi armed forces do not release official casualty figures, but field medics have noted dozens of killed and wounded since the operation to liberate the city began on Oct. 17. Civilians are paying a heavy toll in the battle for Mosul, with nearly 50,000 forced from their homes, most living in displaced persons camps. The Norwegian Refugee Council said Sunday that conditions were worsening for non-combatants, especially over the past week.
"Civilians have told us of horrific stories from inside Mosul," said Wolfgang Gressmann, the group's Iraq director. "They have given terrifying accounts of IS moving them from neighborhood to neighborhood, and from house to house, in tactics identical with being used as human shields."
Meanwhile, a leading U.S.-based rights group released a report alleging that security forces of Iraq's regional Kurdish government had routinely destroyed Arab homes and even some whole villages in areas retaken from the Islamic State group over the past two years.
The Human Rights Watch report said that between September 2014 and May 2016, Kurdish forces advancing against IS destroyed Arab homes in disputed areas of Kirkuk and Ninevah provinces, while Kurdish homes were left intact. It says the demolitions took place in disputed areas in northern Iraq which the Kurds want to incorporate into their autonomous region over the objections of the central government.
Sunni Arab politicians have previously accused the Kurds of seeking to recast the demographics of mixed areas in northern Iraq. The struggle is particularly intense in the oil-rich Kirkuk region. "In village after village in Kirkuk and Ninevah, (Kurdish Regional Government) security forces destroyed Arab homes — but not those belonging to Kurds — for no legitimate military purpose," said Joe Stork, deputy Middle East director at Human Rights Watch. "KRG leaders' political goals don't justify demolishing homes illegally."
All sides fighting in the battle for Mosul have been accused of human rights abuses, with the worst allegations attributed to IS. Kurdish forces have been accused of destroying Arab homes before, with a report last year by Amnesty International alleging that the peshmerga carried out the attacks in retaliation for what they said was the Arab communities' support for IS.
Kurdish authorities say they abide by human rights laws and deny having any strategy to destroy homes. But they say some villages in which the population fought alongside IS have suffered extensive destruction because of the ferocity of the battles.
"There was a large presence of IEDs placed in these areas," said Kurdish official Dindar Zebari, referring to Sunday's report. "I have to say this was a huge cause of the destruction following the liberation process."
Also Sunday, a wave of attacks in and around Baghdad killed at least 23 people and wounded 70 others, inflaming already combustive sectarian tensions in the country. Police and health officials said many of the attacks struck Shiites on their way to an annual pilgrimage, with the deadliest bombing taking place in Baghdad's northern Shaab neighborhood. There, an explosives-laden car parked near a checkpoint killed a policeman and two civilians, and wounded 12 others.
The officials spoke on condition of anonymity as they were not authorized to release information. The capital has seen near-daily bombings since the Mosul operation began, but no large-scale attacks. Militants frequently target security forces and the Shiite majority as part of its campaign to destabilize the country.
Rohan reported from Baghdad. Associated Press writers Sinan Salaheddin in Baghdad, and Fay Abuelgasim in Irbil, Iraq, contributed to this report.