Doubts are emerging about the authenticity of anti-semitic leaflets that were distributed at a synagogue in Ukraine, claiming to be from pro-Russian separatists.

The leaflets were handed out by balaclava-clad men holding the flag of the Russian Federation earlier this week in the eastern city of Donetsk, and plastered to the walls of a synagogue.

They ordered all Jewish citizens over 16 years old to register with the "Donetsk Republic commissar for nationality affairs", and pay a $50 fee.

"Those who refuse to register will be deprived of citizenship and forcibly expelled from the republic and their property will be confiscated," it read.

The leaflet claims to have been issued on the order of Denis Pusilin, self-styled governor of the Donetsk People's Republic, a separatist group that has seized control of several government buildings in Ukrainian region.

US Secretary of State John Kerry condemned the leaflets, describing them as "grotesque" and "beyond unacceptable".

However, doubts have been cast about the source of the flyers, with some arguing that they are fakes, being used to undermine stability in the region still further.

"I think it's someone trying to use the Jewish community in Donetsk as an instrument in this conflict. That's why we're upset," Donetsk chief rabbi Pinchas Vishedski, told journalists on Friday.

Dr Efraim Zuroff of the Simon Wiesenthal Center told the Jerusalem Post that he was sceptical about the leaflets.

"Looks to me like some sort of provocation and an attempt to paint the pro-Russian forces as anti-semitic," Zuroff told the Post.

The Guardian reports that several features of the leaflet cast into doubt its authenticity: Pusilin has stopped short of calling himself the governor of Donetsk, and his official title is Chairman of the Donetsk People's Party, the leaflets are not signed, and the stamp of the party is different to that usually used.

Pusilin has strongly denied his party has any involvement with the leaflets.

The Jewish community sent people to check the address the leaflets order Jews to report to, but there was no one there, community leaders told the Jerusalem Post.

Many prominent Ukrainian Jews supported the protests that led to president Viktor Yanukovych being ousted.

Moscow has accused the new provisional government in Ukraine of being a "fascist junta," and one of the three main leaders of the protest movement, Oleh Tyahnybok, of the nationalist party Svoboda, infamously once said that a "Moscow-Jewish mafia" was ruling Ukraine.

However, Chief Rabbi Yaakov Dov Bleich has blamed a series of anti-semitic attacks in Kiev on the Russians, after Putin proclaimed that Russia's annexation of Crimea was undertaken to protest Russian speaking Ukrainians, Jews, and ethnic minorities, as old tensions resurface.

Pro-Russia protesters take a break inside a regional government building in Donetsk, in eastern Ukraine.
Pro-Russia protesters take a break inside a regional government building in Donetsk, in eastern Ukraine.