The Islamic State jihadist group has claimed responsibility for last week's beheadings of two Syrian activists in southern Turkey, in a video posted to the Internet on Monday.
The video warned "apostates" that "the arm of the Islamic State will reach you, wherever you are."
Ibrahim Abdul-Qadir and Fares Hamadi were found dead in an apartment in city of Sanliurfa on Friday.
The grim video shows Hamadi's body, with his throat slit, in a dark room. Abdul-Qadir was not shown.
Both men are from Raqqa. They had received death threats from IS according to Turkey's state-run Dogan news agency
Abdul-Qader, who fled Syria to Turkey in late 2013, was a founding member of "Raqqa is Being Slaughtered Silently," a collective of activists who document IS atrocities in its self-proclaimed capital of Raqqa in northern Syria.
Abdulqader used a real photo of himself on his Skype profile, and has given several television interviews. He had been tortured in Raqqa by IS.
The activist group was awarded the International Press Freedom Award by the Committee to Protect Journalists (CPJ) earlier this year.
Abdulqader's and Hamadi's slayings will heighten fears about security in Turkey, which was long been accused of allowing IS fighters and supplies to transit freely across its borders into Syria.
Turkey has recently began a wave of raids targeting IS, which it blames for several terrorist attacks, most recently a twin blast that killed 102 people at a pro-Kurdish peace rally in the Turkish capital of Ankara on 10 October. Scores of suspects have been arrested in the operations.
