Doug Stanglin

USA TODAY

Iraqi forces, which drove Islamic militants out of eastern Mosul last month, battled suicide car bombs and bobby-trapped drones Friday near the Tigris river in a bid to rout fighters from the western half of the country's second-largest city.

The advances in the Mamun neighborhood came a day after special forces joined the fight in the western sector against entrenched fighters from the Islamic State, also known as ISIL or ISIS.

Iraqi authorities declared the city’s eastern half “fully liberated” from the Sunni militants in January, three months after launching the operation to take back Mosul.

One Iraqi colonel leading the operation told the BBC that western Mosul "is where the real fighting starts."

An Associated Press team near the front line saw at least four wounded special forces’ members and the bodies of three soldiers, suggesting more intense fighting than the previous day. The Iraqi military does not release official casualty information.

The fighting is complicated by the narrow streets, and alleys preclude the use of tanks and armored vehicles in western Mosul, which is divided by the Tigris. Advancing Iraqi special forces also often face suicide car bombs and armed drones unleashed by militants.

"There is a resistance there. The drones are particularly annoying today," Major General Sami al-Aridi, a senior CTS commander, told Reuters.

In addition, the United Nations estimated about 750,000 civilians are trapped in the western neighborhoods, according to the AP.

Earlier Friday, the spokesman of the Joint Military Operation Command, Brig. Gen. Yahya Rasool, said Iraqi forces recaptured the military base as well as the adjacent airport in southwestern Mosul.

Both the Ghazlani military base and the airport will serve as a base of operations as Iraqi forces launch subsequent pushes into western neighborhoods.

Iraq’s Prime Minister Haider al-Abadi, meanwhile, announced Iraq’s air force strikes on Islamic State targets inside Syria for the first time Friday. The strikes on the towns of Boukamal and Husseibah across the border were in response to recent bombings in Baghdad claimed by Islamic State fighters linked to the militants’ operations in Syria, he said.

An Iraqi air force commander said F-16 warplanes carried out the "successful" strikes in Syria at dawn, the AP reported. The commander, who spoke on condition of anonymity because he was not authorized to talk to media, said the prime minister ordered the strikes.

Contributing: Associated Press