A PKK militant stands at a barricade as some of thousands of people flee from the historic Sur district of the mainly-Kurdish city of Diyarbakir, Turkey.

One Turkish soldier was killed and another wounded in clashes with Kurdish rebels trying to cross the border from Syria into southeast Turkey, the military said Wednesday.

Turkish security forces opened fire Tuesday on seven militants from the Kurdistan Workers Party (PKK) in the Cizre district of Sirnak province as they were entering Turkey from Syria, the army said in a statement.

Two soldiers were heavily wounded in the ensuing clashes and one of them later died in hospital, it added.

Cizre has been under a controversial curfew for six weeks as the army pursues a relentless campaign against rebels of the PKK which activists claim has cost dozens of civilian lives.

The town lies just across the border from an area in northern Syria that is controlled by the Syrian Democratic Union Party (PYD), which Ankara considers to be the affiliate of the outlawed PKK.

The border incident came as Turkey’s foreign ministry on Tuesday summoned the U.S. ambassador to Ankara John Bass after a U.S. State Department spokesman angered Ankara by saying that Washington did not consider the PYD as a terrorist organization.

Turkish President Recep Tayyip Erdogan had on Sunday urged Washington to choose between Turkey and the “terrorist” Syrian Kurds.

The U.S.-led coalition fighting ISIS in Syria and Iraq has worked closely with the YPG, the military wing of the PYD, since it launched air strikes in Syria in September 2014.

Turkey fears the creation of an autonomous Kurdish region in Syria — similar to the Kurdish region in northern Iraq — would spur the separatist ambitions of Turkey’s own Kurds.

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