Isis have released a new video reportedly showing the execution of five Syrian media activists.
The five men were abducted in October, according to the UK-based Syrian Observatory for Human Rights (SOHR).
The Observatory said the men were killed in December for their coverage of events in the Isis-held city of Deir el-Zor in eastern Syria.
The graphic video also includes a narrator talking about the media war Isis faces, while warning against reporting to "the crusaders" and "enemies of god".
Rami Abdurrahman, the founder of SOHR, told AP the news of the men's detention and death had been withheld as no bodies had been found. The activists' families had feared retribution for reporting their deaths.
One of the men featured in the video, 28-year-old Sami Jawdat, had been supplying information to the Observatory since the civil war broke out in 2011, according to SOHR.
Mr Abdurrahman added that Jawdat continued to provide information after Deir el-Zor was captured by the so-called Islamic State in 2014. Jawdat was reportedly detained on a number of occasions.
After learning about the activists' abduction and killing, Mr Abdurrahman say the group now advise activists to refrain from taking photos and videos in Isis-held areas.
Syria is third deadliest country for journalists with at least 95 journalists killed in the country since 2011, according to the Committee to Protect Journalists.
