The extremist Islamic State (IS) organization on June 26 published a video showing the execution-style killing of five Syrian media activists captured by the group's militants last year.
The Britain-based Syrian Observatory for Human Rights says the victims seen in the graphic footage, which was posted on the blog of the extremist organization's Al-Bayan radio, were abducted in October and are believed to have been killed in December.
The monitor's head, Rami Abdurrahman, said they were believed to have been killed for their coverage of the Syrian conflict in the city of Deir el-Zour, around half of which is controlled by IS forces.
He said one of those killed supplied information to the Syrian Observatory for Human Rights.
One of the activists says in the video that he contributed to the New York-based Human Rights Watch, while another said he had done work for Al-Jazeera.
Neither of those organizations had commented publicly on the video as of June 26.
IS militants have previously claimed to have killed several media activists working secretly in IS-controlled areas in Syria, where almost no international media organizations have journalists due to the dangers of reporting there.