BAGHDAD (AP) — Residents of Iraq's Islamic State-held city of Mosul said Wednesday that an airstrike disabled the city's last functioning bridge across the Tigris River, forcing residents to cross the river in boats and further disrupting the IS group's movement.

The residents, who spoke to The Associated Press on condition of anonymity fearing for their safety, said the airstrike happened at dawn Monday. Iraqi and U.S.-led international coalition officials were not available to comment.

Activists from inside Mosul published pictures Tuesday night of the metal bridge, known as the Old Bridge, showing its twisted girders sinking into the water as boats were seen ferrying the residents from both banks. The bridge, which was built during the reign of King Ghazi in the 1930s, is considered one of the city's iconic landmarks.

The northern city of Mosul had five bridges spanning the Tigris River, which runs through the center of the city. Four of them have now been bombed in airstrikes since the massive government military operation began on Oct. 17, while one was disabled weeks before the operation began.

The Tigris River runs through the center of Mosul, and until now most of the fighting has been on the eastern bank. Iraqi forces are expected to use pontoon bridges when they reach the river as they have done in previous military operations in other areas.

Fighting on all fronts, but centered mainly on Mosul's eastern edge, has slowed recently as suicide car bombings, snipers and concern over the safety of civilians have hampered the Iraqi troops' advance toward the city center.

In a press conference on Tuesday, Iraqi Prime Minister Haider al-Abadi said IS militants have launched more than 900 car bombs against Iraqi troops so far during the Mosul operations, but didn't give details on how many were driven by suicide bombers or were blown up before reaching their targets.

Al-Abadi added that the offensive "is continuing ... God willing, there will be good news in the coming days."

Mosul, about 225 miles (360 kilometers) northwest of Baghdad, is Iraq's second-largest city and the last major IS urban bastion of their self-styled caliphate in the country. It fell into the hands of IS militants during their June 2014 onslaught that left the group in control of large swaths of northern and western Iraq.