A conservative group has highlighted incidents of antisemitism and anti-Israel activity at the Occupy Wall Street protest.

The demonstration, which began last month and has now spread from Manhattan to other US cities and most recently London, has attracted a wide demographic. Jewish campaigners have held a Yom Kippur service in the heart of the protest, while a succah has been set up there this week.

But according to the right-wing Emergency Committee for Israel, there have also been several incidents of visibly anti-Jewish behaviour, with a protester complaining of a "conspiracy in this country where Jews control the media, finances".

In video footage from the demonstration, people are shown holding signs reading "Hitler's Bankers" and "Gaza supports the occupation of Wall Street". A man wearing a kippah is jeered at and told: "You have the money…Go back to Israel".

However, in another clip, a man holding a sign attacking the "Zionists who control Wall Street" is challenged by several protesters.

The Anti Defamation League said it would monitor the demonstrations to ensure that they were not hijacked by extremists.

Abraham Foxman, the ADL's national director, said that he did not think the conspiracy theories were representative of the larger views of the movement.

But he added: "It is still critical for organisers, participants and supporters of these rallies to condemn such bigoted statements clearly and forcefully.

"History demonstrates time and again how economic downturns can embolden antisemites to spread malicious conspiracy theories and promote stereotypes about Jews and money. As a consequence, these statements must not be left unchallenged."