Syria ceasefire Turkey air strikes
Turkish military announced Monday that its planes attacked the Islamic State group in northern Syria and hit three targets used by it — a shelter, an ammunition store and the group’s military headquarters. GOKHAN SAHIN/GETTY IMAGES

Nine Turkey-backed Syrian rebels were killed and 32 were wounded on Thursday fighting in an operation to push Islamic State militants away from the border area in Syria, Turkey's military said on Friday, indicating a fresh surge in clashes.

The rebels have seized control of just over 1,000 square km (386 square miles) of territory from the Islamic State militant group in the offensive, dubbed "Euphrates Shield," since it was launched on Aug. 24, the military said.

Turkish warplanes hit 18 targets in the region over the past 24 hours, destroying 15 buildings used by Islamic State fighters, while U.S.-led coalition warplanes killed three of the militants in air strikes, the statement said.

Turkey's entry into Syria has raised concerns of a further escalation in an increasingly fraught regional conflict.

Ankara says its efforts to cleanse its border region of Islamic State militants are legitimate under international law as self-defense after months of rocket attacks and bombings in cities along the boundary.

President Tayyip Erdogan has also made it clear that Turkish forces are in Syria to prevent the Syrian Kurdish YPG militia, which is backed by the United States to fight Islamic State, from expanding areas under its control.

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