Story highlights "It's important for everyone to know its not true," Ukrainian rabbi says

Masked men handed out the fliers in front of a Donetsk synagogue, Jewish community says

Jewish leaders call it a "provocation ... full stop"

The U.S. ambassador in Kiev calls the leaflets "chilling" and "almost inconceivable"

U.S. officials Thursday denounced what one called a "grotesque" leaflet ordering Jews in one eastern Ukrainian city to register with a government office, but the Jewish community there dismissed it as a "provocation."

The fliers were handed out by masked men in front the main synagogue in Donetsk, where pro-Russian protesters have declared a "People's Republic," Jewish leaders there said. The document warned the city's Jews to register and document their property or face deportation, according to a CNN translation of one of the leaflets.

Geoffrey Pyatt, the U.S. ambassador to Ukraine, told CNN's "The Lead with Jake Tapper" that a respected Jewish leader in Ukraine showed him a photograph of one of the leaflets. He called the document "chilling."

And in Geneva, where diplomats held emergency talks on the Ukrainian crisis, U.S. Secretary of State John Kerry called the leaflets "grotesque" and "beyond unacceptable."

But the Jewish community statement said relations between the Jews of Donetsk and their neighbors were amicable, and the self-proclaimed head of the "People's Republic," Denis Pushilin, denied any connection to the fliers.

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Pushilin told CNN the handwriting on the flier wasn't his, and the title attached to his name was not one he uses. It wasn't clear who had distributed the leaflets, but the chief rabbi of nearby Dnipropetrovsk said, "Everything must be done to catch them."

"It's important for everyone to know its not true," said the rabbi, Shmuel Kaminezki. "The Jews of Donetsk will not do what the letter says."

The reports come as Ukraine's Western-backed interim government has been struggling to contain uprisings by pro-Russian political movements in several eastern cities, with both sides invoking the historical horror of Nazism in their disputes. Pyatt told CNN that radical groups may be trying to stir up historic fears or create a provocation to justify further violence.

"It's chilling. I was disgusted by these leaflets," Pyatt said. "Especially in Ukraine, a country that suffered so terribly under the Nazis, that was one of the sites of the worst violence of the Holocaust. To drag up this kind of rhetoric is almost beyond belief."

The leaflets were handed out on Tuesday, during the Jewish holiday of Passover, the Jewish community statement said. They stated that registration was required because Jewish leaders had supported the "nationalists and bandits" in Kiev, where a popular revolt ousted pro-Russian President Viktor Yanukovych in February.

"All citizens of Jewish nationality over age of 16, living on territories of Donetsk People's Republic, have to register with DPR commissioner of nationality before May 3rd, 2014 at the Donetsk Regional Administration, room 514, registration fee is $50," read a photographed copy of the leaflet translated by CNN. "Must have in person $50 cash, passport, all available IDs, and documentation of ownership of real estate and transportation."

Where unrest has occurred in eastern Ukraine

The men also hung posters with the same message, it said.

"Who is behind this is an open question," Rabbi Pinkhas Vishedski said in the statement. But he said the act was a provocation "and should be treated accordingly ... full stop and end of topic."

Provocation or not, the U.S.-based Anti-Defamation League condemned their distribution and what it called their "cynical and politically manipulative" exploitation of anti-Semitism.

"We are skeptical about the flier's authenticity, but the instructions clearly recall the Nazi era and have the effect of intimidating the local Jewish community," ADL Director Abraham Foxman said in a written statement.

Pyatt said that in Kiev, where the Jewish community is a vital part of political life, there is "no sympathy for this approach."

"It's almost inconceivable that this kind of thing could be happening in the 21st century," Pyatt said.

And Kerry said all parties at the Geneva talks unanimously condemned anti-Semitism and other forms of religious intolerance.

"Any of the people who engage in these kinds of activities -- from whatever party or whatever ideology or whatever place they crawl out of -- there is no place for that," he said.