The Islamic State (Isis) has released a new execution video which purportedly shows five journalists being brutally murdered in Syria by the extremist group.

The footage shows two of the five journalists blown up with explosives packed into their cameras and laptops; both are chained to a metal railing with cameras around their necks, which are later detonated.

Another journalist is seen bound to a door and choked with a chain. A fourth journalist is killed with a "sharp object" while a fifth has his throat slit with a knife, according to the UK-based Syrian Observatory for Human rights, the Daily Mail reported.

The journalists were accused of "acting against the IS communicating with outside parties and receiving funds, and other charges".

The video also warns reporters to not cover issues on the "crusaders" and "enemies of God", adding that journalists who do report on IS, even those residing in Europe, may also be targeted by the extremist group.

According to Rami Abdurrahman, the founder of the Observatory, the five journalists were abducted in October 2015 and were believed to have been murdered in December, for their coverage on the events taking place in eastern Syria, in the city of Deir el-Zour, which is partly occupied by IS.

Abdurrahman said the deaths of the journalists were not announced as no bodies had been recovered, and the families feared reporting the deaths for fear of reprisals. Abdurrahman said one of the activists, Sami Jawdat, 28, had been providing the Observatory with information since the civil war first erupted in 2011 and continued to send in information even after IS occupied a sizeable portion of Deir el-Zour in 2014. Jawdat was also reportedly apprehended by IS more than once in the past.

The video features each of the journalists detailing their action when reporting in the area. One journalist is heard saying that he was a reporter for Al-Jazeera, while another says he was a contributor to the New York-based Human Rights Watch.

According to a report by the Committee to Protect Journalists (CPJ), Syria is one of the most dangerous places in the world for a journalist. In 2015 alone, of the 69 journalists killed for their work, 60% were murdered by extremist groups like IS and Al-Qaeda.