The beheaded bodies of a Syrian activist opposed to the Islamic State (ISIS) group and his friend were found early Friday in the southern Turkish city of Sanliurfa, his group told AFP.
Ibrahim Abdul Qader, 20, and his friend Fares Hamadi "were found beheaded at the friend's house this morning," Abu Mohammad, a founder of the "Raqa Is Being Slaughtered Silently" group, said via the Internet.
The group, which documents abuses in areas under ISIS control in Syria, accused the jihadist organization of the murders on its Facebook page.
If ISIS was indeed behind the attack in Turkey it would indicate their strong presence over the border from Syria, despite Turkey's alleged campaign against ISIS which has instead targeted Kurdish forces to a far higher degree, indicating the true goal of Ankara.
Turkey's role regarding ISIS was placed in question after documents were seized in July showing Ankara cooperated with ISIS by taking part in ISIS's cross-border black market oil sales.
According to Abu Mohammad, both men were from Raqa city, the de facto capital of ISIS in Syria. Hamadi was also in his early 20s.
Abdul Qader had escaped to Turkey a little over a year ago.
Members of the activist group had been killed inside Syria in the past, but this is the first time a member had been killed outside the country, Abu Mohammad added.
Turkey's Dohan news agency reported Friday that "two Syrian journalists were beheaded" in Sanliurfa, and that seven Syrians had been arrested by Turkish police.
Sanliurfa is 55 kilometers (35 miles) from Turkey's border with Syria's Raqa province, a major ISIS stronghold in the country.
Turkey has long been accused by Syrian opposition activists, Kurdish fighters and sometimes even Western partners of allowing ISIS members to slip back and forth across its 911-kilometer (566-mile) frontier with Syria.
Bloody bomb attacks in southern Turkey, including an attack in July that claimed 32 lives in Suruc, have been blamed on ISIS, though the group has never claimed responsibility for the blasts.
AFP contributed to this report.