MOSUL, Iraq — The Iraqi advance into Mosul’s western half slowed Saturday as combat turned to urban warfare and Iraqi forces met stiff resistance from the Islamic State group.

Hundreds of civilians poured out of Mosul on foot following the advances, but the vast majority of 750,000 estimated to still be in the city’s west remain trapped. The trapped civilians describe deteriorating humanitarian and security conditions.

Special forces Lt. Gen. Abdul-Wahab al-Saadi said that his troops are “moving very slowly” and that militants are responding with car bombs, snipers and dozens of armed drones. The drones have caused relatively few deaths but have inflicted dozens of light injuries that have disrupted the pace of ground operations.

Similar to the way operations in eastern Mosul initially unfolded, in west Mosul, the Islamic State repeatedly brought Iraqi convoys to a halt Saturday with small teams and a handful of car bombs.

Al-Saadi said the Mamun neighborhood was particularly difficult because its streets are not organized in a grid. This makes it more difficult for his men to set up roadblocks to stop car bombs, a difficulty that foreshadows obstacles Iraqi forces expect to face in the narrow alleyways of western Mosul’s historic district.

But al-Saadi said he expects the pace to increase after Iraqi forces retake territory and infrastructure on Mosul’s southwestern edge — which will enable them to shorten supply lines and link up with forces in the city’s east.

Along the road beside al-Saadi’s base of operations, hundreds of civilians fleeing Mosul walked slowly past, many with sheep, cows and goats in tow. Nearly all of the hundreds who fled Saturday trekked more than 3 miles from the city’s edge to a small village serving as a screening center.

Dozens of families gathered against a crude cinder block wall at the screening center south of Mosul. Intelligence officials at the site said after documents were checked families would be moved into nearby abandoned houses or newly erected camps for the displaced.

Many of those fleeing said they were from villages outside Mosul and had been forced to march to the city more than four months ago to serve as human shields.

Groups of men were screened at the site against a database of Islamic State suspects, and two prisoners were dragged past the crowd and into an abandoned building.

Also Saturday, a Kurdish journalist working for the Rudaw news organization, Shifa Gerdi, was killed covering the Mosul operation. A number of journalists have been killed since the operation began last year and in October an Iraqi television journalist was killed covering the battle.