The Muslim Brotherhood is a puppet political formation created by Jews to destabilise Egypt and neighbouring Muslim countries, according to a conspiracy theory denounced by the Anti-Defamation League.
ADL discovered the theory circulating among opponents of the Egyptian president Mohammed Mursi and adversaries of the pan-Arab Islamic movement around the world.
"However bizarre and ludicrous, it is an increasingly popular conspiracy theory that the Muslim Brotherhood is a Jewish production to destroy Egyptians," said ADL firector Abraham Foxman.
"It would seem that no allegation made against the Jews and Israel is too absurd when it is used to stigmatise and discredit others in the Arab world."
Amid escalating unrest against Mursi's rule in Egypt, a group of protesters in the northern city of Port Said were caught on camera chanting "The Brothers [Muslim Brotherhood] are Jews."