MOSUL, Iraq -- After weeks of airstrikes and artillery fire, Mosul's al-Salam hospital is little more than a burnt-out shell. Retaken from the Islamic State group by Iraqi forces this month, the building's top floors were almost completely destroyed. The gardens around the complex are strewn with medical records and supplies. Bright blue hospital bedsheets hang from nearby trees.

The hospital in eastern Mosul was the scene of one of the most significant setbacks for Iraqi troops in the nearly 3-month operation to retake Iraq's second-largest city. On Dec. 6, after advancing too quickly, Iraqi forces found themselves surrounded by IS fighters in the hospital complex. Pummeled by wave upon wave of militant counterattacks, dozens were killed and wounded, according to Iraqi military and hospital officials, eventually forcing a withdrawal.

Some Iraqi army officers blamed the setback on insufficient air support by the U.S.-led coalition. Others faulted poor leadership and a lack of coordination among the many disparate Iraqi forces participating in the Mosul offensive, including tribal and militia fighters who maintain their own command structures.

Following the December withdrawal, Iraq's elite rapid-response unit joined the Iraqi army on Mosul's southeast front and the U.S.-led coalition increased its air campaign, despite an initial reluctance to use airstrikes against IS in the vicinity of the hospital.

Over the past month, coalition planes dropped 25 bombs on the hospital complex, according to a Pentagon statement provided to The Associated Press. After weeks of static front lines, the renewed air and ground assault brought Iraqi forces to the edge of the Tigris River. Since the Mosul operation was launched in October, Iraqi forces have slowly clawed back about a third of the city.

"We have more experience in urban areas," said Brig. Gen. Mehdi Abbas Abdullah, a commander of the rapid-response unit, explaining why his forces were able to eventually retake the hospital. Before joining the Mosul fight, he led men in Fallujah and Khaldiya in Iraq's Anbar province.

But one of his men said air power rather than ground forces played the key role.

"Honestly, the battle was 75 percent fought from the air," said Sgt. Maj. Hassan Ali Jalil, acknowledging the military's continued reliance on coalition airstrikes despite months of coalition training.

The Iraqi army's 9th division, which led the fight for the hospital until being forced to withdraw last month, is an armored unit designed to fight on open terrain rather than in dense urban environments.

On Tuesday, half a dozen destroyed Iraqi army tanks filled a parking lot beside the hospital. The large, cumbersome vehicles were captured by the IS fighters who were moving around the battlefield, across rooftops and through tunnels connecting the basements of buildings.

The commander of the 9th division, Lt. Gen. Qassim Jassim Nazal, visited the hospital complex Tuesday for the first time since he was forced to withdraw last month. Walking past the bombed-out buildings, he asked to be shown the destroyed vehicles left behind by his unit.

"This is like a revenge to return to this place," said Nazal, adding that his men were unable to fight back against the IS fighters and the waves of car bombs they unleashed without heavy air support. "They were not normal car bombs. Each one was like an atomic blast," he said.

The hospital basement had been transformed into an IS bunker. Dozens of mattresses filled rooms, ammunition and body armor lined hallways and Islamic religious texts were piled atop shelves. There was no evidence to suggest the complex was being used as a hospital to treat civilians at the time of the attack: medical records viewed by an AP team at the scene were dated more than a year ago.

Coalition spokesman U.S. Army Col. John Dorrian said it was "clear" the hospital was being used by IS as a headquarters and was no longer being used as a facility to treat civilians.

"If the enemy is going to use facilities like (hospitals) as a storage place for weapons or as an operations headquarters, we will strike those kinds of facilities," Dorrian said, adding that the practice is consistent with the laws of armed conflict.

Retaking the hospital has allowed Iraqi forces to punch deeper into Mosul and reach the edge of the Tigris River that divides the city's east and west.

The city's Yarimjah neighbourhood, just a few hundred yards (meters) from the banks of the Tigris, is now the front line in the Mosul fight. Children played in its narrow streets on Tuesday, scattering and hiding at the sound of mortars and rockets flying overhead.

"We learned what that sound means," said 13-year-old Hamid Mahmood, playing in front of his home with his younger brothers.

Over the past three months, Saif Ahmed, 23, estimates that more than 30 people from his neighbourhood alone have died in the clashes between Iraqi troops and IS fighters. In just the past week, his family has buried his sister-in-law and her infant daughter. The woman was killed in a mortar attack. Days later, her 10-day-old baby died after contracting diarrhea.

Iraqi Capt. Mazin Mohammad, stationed in Yarimjah, said Iraqi forces there are especially vulnerable to mortar attacks because of the open fields separating his men from IS positions on the far bank of the Tigris.

"It's an open area and they can see us coming," he said.