Israel's Foreign Ministry has stressed that a film said by some to have triggered fatal rioting in Libya and Egypt had not been made with Israel's involvement.
Foreign Ministry spokesman Yigal Palmor stated unequivocally that the film, made by a man who indentifies himself as an Israeli Jew, "has nothing to do whatsoever with Israel".
The "Innocence of Muslims," which shows the prophet Mohammed in an unfavourable light, was produced by Sam Bacile, who has described himself as a 56-year-old California real estate developer. Although the low-budget film initially appeared online a few months ago, it was circulated this week and has been blamed by some for encouraging a pro-Islamist riot in Benghazi that left the US ambassador and three other embassy workers dead.
But according to Steve Klein, a Christian activist connected to the film, the name could be a pseudonym and the man behind it may not be Jewish.
Other reports have suggested that Mr Bacile, who is understood to have gone into hiding following the furious reaction to the film, is an entirely made-up identity. Another view is that he is a Coptic Christian called Nakoula Basseley Nakoula.
"This guy is totally anonymous. At this point no one can confirm he holds Israeli citizenship," said Mr Palmor.
"He didn't do it for us, in coordination with us or through any sort of channel connected to Israeli institutions," he added. "He's a complete loose cannon, and an unspeakable idiot."
He said the content of the film betrayed "intolerable intolerance" on the part of its producer.
Rabbi Abraham Cooper, associate dean of the Simon Wiesenthal Centre, a human rights organisation based in Los Angeles, urged the media to find out the identity of the filmmaker, pointing out that if he was not Jewish but had been labelled so by those involved, it could be very dangerous for Jews.
He said such a false claim that the filmmaker was Jewish could be "a classic antisemitic blood libel" and added: "With what is going on in the world - all the violence, emotion and hatred you see toward Americans and Israelis at these demonstrations - to then catapult what might be a nonexistent Jewish element could lead to violence against Jews."
He added: "I would hope the wire services that were involved in spreading this allegation will belatedly do their due diligence and get to the bottom of who said this, why they said it and then hold them accountable."
In a statement, the Muslim Council of Britain commented: "We hope that others will join us in condemning both the violence in Egypt and Libya, and the irresponsible actions of the film's Israeli-American producer."