Iraqi security forces fight Islamic State militants in western Mosul, Iraq, on March 6. (Khalid Mohammed/AP)

Iraqi forces claimed to have recaptured Mosul’s main government compound from the Islamic State on Tuesday, marking a strategic and symbolic advance into the northern city at the heart of the militant group’s self-proclaimed caliphate.

In a surprise pre-dawn raid, elite police units seized the government buildings in the Bab al-Tob neighborhood of western Mosul, including a central square where the militants carried out public executions. Commanders said that they faced limited resistance and that the group’s grip on the city is crumbling, although there were reports of intense counterattacks. 

Mosul, home to more than a million people, is the last major city that the Islamic State controls in Iraq and the biggest population center it seized during a large-scale land grab in 2014. Tens of thousands of Iraqi forces have waged a bitter campaign since mid-October to retake the city, suffering heavy casualties as the militants have launched car bombings and other attacks.  

The pace of the Iraqi advance has picked up in recent weeks after police forces led a push into the city’s western side, but the human toll also is mounting as the fighting moves through densely populated neighborhoods. The government estimates that about 10,000 people are fleeing each day. 

Airwars, a Britain-based organization that tracks allegations of civilian deaths in the fight against the Islamic State, said Tuesday that such casualties appear to have escalated this month, with hundreds reported killed in what it described as a “bloody harbinger.” 

And despite the gains for Iraqi forces, the battle is far from over. Around half of the western side of the city is still held by the militants, said Brig. Gen. Yahya Rasoul, a spokesman for Iraq’s joint operations command. That includes the packed and narrow streets of the old city. The eastern half of Mosul was recaptured earlier this year. The city is split into two by the Tigris River.

“Reaching here is a message to the people of Mosul that the enemy that used to suffocate them is officially finished,” said Brig. Gen. Abbas al-Jubory, chief of staff of the Iraqi police’s emergency response division, which led the attack toward Bab al-Tob. He denied there had been any counterattack, but the Associated Press reported that troops had become cut off inside the compound after an initial rapid advance.

He compared retaking the square there, the backdrop to many Islamic State execution videos, to the Americans reaching Firdos Square during their 2003 invasion of Iraq, when a towering statue of Saddam Hussein was pulled down.

Col. John L. Dorrian, a spokesman for the U.S.-led coalition in Baghdad, which has been closely supporting the fight with airstrikes and expertise, said retaking the Mosul government buildings provides Iraqi forces with a staging area to launch an assault on the old city. “Some of the streets are too narrow for vehicle traffic,” he said. “That sets them up for a tough fight.”

Islamic State militants have been blocking side streets with booby-trapped cars to “channel” the Iraqi advance in the direction of their choosing, Dorrian said. However, suicide car bombings have been less ferocious than earlier in the offensive, he said. “They don’t have many of the ‘Mad Max’-style up-armored vehicles,” he said. 

Jamming equipment also has helped eliminate the threat of grenade-dropping drones, he said. 

Although individual drone attacks had limited impact, the sheer number of them was waylaying forces. There were 73 Islamic State drone attacks on the first day of the offensive targeting the western side of the city, according to Lt. Gen. Sami al-
Aridhi, a commander with Iraq’s counterterrorism forces. 

The government estimated that about 750,000 civilians remained in the western half of the city when the offensive began, with the militants preventing many from leaving their homes. Around 50,000 people have fled in the past two weeks, according to the United Nations, which says it is ill-equipped to support them.

People are arriving in camps with only the clothes they were wearing, said Wolfgang Gressmann, country director in Iraq for the Norwegian Refugee Council. “They are cold, exhausted and hungry — crying from either exhaustion or trauma or both,” he said. “We fear what will happen as the wave continues.”