"Security forces caught a Daesh [acronym for Islamic State] member [on Wednesday] in Gaziantep. A judicial process has been started," the Turkish General Staff said in a statement on its website.
According to a separate statement on Monday, four suspected Islamic State affiliates were seized in Gaziantep province's city of Oguzeli by Turkish security forces.
Turkey shares its longest common border with Syria. Since the beginning of the Syrian Civil War in 2011, the flow of jihadists seeking to join Islamic State on the Syrian-Turkish border has increased.
The Islamic State is a Sunni group that has been fighting in Syria and launched an offensive in Iraq in June 2014. The group has taken over large parts of the country, with the goal of seizing Baghdad. Also in June, the group announced the establishment of a caliphate on the Iraq-Syria border.