An Iraqi soldier waves the national flag as security forces patrol on the eastern side of Mosul on Jan. 18. (Khalid Mohammed/Associated Press)

Iraqi forces pushed deeper Wednesday into former Islamic State-held areas of Mosul, extending government control over eastern parts of the city but still facing a fight against the militants in western districts across the Tigris River.

Iraqi Prime Minister Haider al-Abadi hailed the advances as another step toward “liberation and total victory” in the strategic northern city, which had been the stage for months of battles seeking to drive the Islamic State from its main urban foothold in Iraq.

The militants are now left with only a handful of neighborhoods on the city’s eastern side, according to military officials.

Across the Tigris River, however, the Islamic State retains firm control over city’s western half — home to key government buildings and even more densely packed with civilians.

Authorities said the latest advance was spearheaded by Iraqi counterterrorism units that have endured heavy losses during the three-month campaign to reclaim Mosul.

Gen. Talib al-Kinani, commander of Iraq’s counterterrorism service, said the units faced Islamic State attacks including “more than 300 car bombs and many suicide bombers.”

[After slow start, Iraqi forces pick up pace in Mosul]

“Today is the day of joy and victory,” Kinani said.

He predicted that the campaign in the city’s western half would be “easier.” Bridges to the western side of the city have been destroyed, making it difficult for militants to add reinforcements and crucial supplies.

As Iraqi forces make headway, more advisers have arrived from the U.S.-led coalition assisting government troops. Airstrikes, meanwhile, have attempted to disrupt car bombs inside the city.

Iraqi officials said their campaign has been slowed in recent months by the presence of civilians.

Car bombs, the deadliest weapons deployed by the Islamic State, pushed the casualty rate among Iraqi counterterrorism forces to as high as 20 to 25 percent at one point, a general, who spoke on the condition of anonymity because of the sensitivity of the subject, told The Washington Post last week.

Officials said the casualty rate has decreased following a two-week pause in fighting late last month during which Iraqi forces received new fighters and equipment.

“We are using new tactics and strategies, and we have reduced the casualties during the second phase,” Brig. Gen. Yahya Rasoul, spokesman for Iraq’s Joint Operations Command, said last week.

Mustafa Salim contributed to this report.

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