Al Jazeera has apologised after it published a story which suggested the videos showing the beheading of US journalists James Foley and Steven Sotloff were fake.
The article, which featured on Al Jazeera Arabic, the sister network of Al Jazeera English, claimed the videos of the murders were "unconvincing" and Foley was giving a "theatrical performance".
The article also claims that Foley may never have been kidnapped by Isis militants and questioned if it is even him that appears in the graphic video.
"Foley was playing the role of champion not the victim only, for he recites a lengthy statement in peerless theatrical performance, and it seems from tracking the movement of his eyes that he was reading a text from an autocue," the article said.
It added the masked man who is filmed with Foley, known as Jihadi John, does not have the features of common jihadist figures, but instead is "rather similar to a Hollywood actor".
The news site aploigised and has now withdrawn the article "in respect to families of the victims and as we share their grief".
Al Jazeera's managing director, Yasser Abu Hilalah, said: "Al Jazeera Arabic's website decided to retract an inaccurate article that questioned the legitimacy of Foley and Sotloff's beheading videos after a theory surfaced on a number of American social media sites claiming they were produced as a pretext ahead of a US invasion of Syria.
"We want to take this as an opportunity to reiterate Al Jazeera previous position in condemning the kidnapping of the two journalists and condemning their killing as a heinous crime.
"We would like to also renew our call for the release of all kidnapped journalists, who are only carrying out their professional duty in seeking truth and providing a fair and comprehensive account of events and issues.
"Al Jazeera had previously issued a statement before the killing of Sotloff, appealed to the kidnappers to release him and adopted Sotloff's mother's message appealing to the kidnappers to release him.
"We, in Al Jazeera, would like to emphasise our policy of supporting the freedom of journalists and to protect them from any harm anywhere around the world."
A forensic science company who work with British police previously suggested the execution may have been staged and that the execution may have happened off camera.
The forensic analyst said Foley appears to have to repeat a line during his speech and the lack of blood before the video fades to black was inconsistent with a knife wound to the neck.
However, the company, which requested anonymity, added: "No one is disputing that at some point an execution occurred."