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Laura Eldeiry, a spokeswoman for Radiohead, said that the band would not be playing a show at Zuccotti Park on Friday that had been announced by Occupy Wall Street’s organizers.

“It’s definitely not going to happen,” Ms. Eldeiry said. “It’s a false rumor.” She said that the band had nothing to do with the announcement and that a show “was never planned.”

At 3:30 p.m., Occupy Wall Street’s spokesman, Patrick Bruner, sent out a rueful e-mail blast: “I got hoaxed. Radiohead was never confirmed. Completely our fault. Apologies. The band were victims in this hoax as well.”

A while later, the band itself issued its first Twitter post on the matter. “We wish the best of luck to the protesters there,” @radiohead wrote, “but contrary to earlier rumours, we will not be appearing today at #occupywallstreet.”

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The organizers of Occupy Wall Street set off a frenzy of excitement, confusion and conflicting speculation on Friday afternoon when they announced that Radiohead would play a “surprise” concert at 4 p.m. Friday at the protest headquarters in Zuccotti Park.

A spokeswoman for Radiohead, Laura Eldeiry, said in an e-mail, “We can officially say this is not happening.” But the meaning of “officially” in the slippery informational context of a protest movement was not immediately clear.

The prospect of such a show, in a three-quarter acre park in the midst of the dense financial district, raises serious questions about logistics and crowd control.

The head police spokesman, Paul J. Browne, did not immediately return a call seeking comment on the concert, the police’s plans to handle it, or whether permits have been requested.

The band has been in New York this week to play shows at Roseland Wednesday and Thursday.

The protesters, who have been marching for the past two weeks against corporate profits, bank bailouts and the growing income gap, have gained allies in recent days, including labor unions that have sent money and marchers.

Incidents of police officers, including a deputy inspector, using pepper spray and other harsh tactics against the protesters have helped raise the movement’s public profile.

But the arrival of Radiohead, a British band with a history of support for left-wing movements, offers an immediate spectacle and reflects the interest around world for the anti-Wall Street protests.

With a background of strong police response to the protesters, the “surprise” concert threatens to create chaos downtown –- a rock music trope, whether the band Rage Against the Machine playing in Los Angeles at the Democratic National Convention in 2000; a U2 rooftop concert in 1987 and the Beatles rooftop “Let It Be” London show, the mother of all impromptu concerts.