BAGHDAD — Iraq’s air force struck Islamic State targets inside Syria for the first time on Friday as Iraqi troops on the ground pushed into western Mosul, the last major urban stronghold held by the Sunni militant group in Iraq.

Iraq’s Prime Minister Haider al-Abadi announced the airstrikes in a statement, saying the air force hit towns of Boukamal and Husseibah across the border and came in response to recent bombings in Baghdad claimed by IS and linked to the militants’ operations in Syria.

Meanwhile, Iraqi forces pushed into the first neighborhood of western Mosul and took full control of Mosul’s international airport and a sprawling military base on the southwestern edge of the city, according to Iraqi officials.

The territorial gains mark the first key moves in the battle, now in its sixth day, to rout IS militants from the western half of Mosul, Iraq’s second-largest city.

The push into Mamun neighborhood was followed by intense clashes with IS militants, according to an Iraqi special forces officer on the ground, who spoke on condition of anonymity in line with regulations.

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.