DONETSK, Ukraine — Worshipers at the Bet Menakhem-Mendl synagogue in this eastern Ukrainian city confronted a horrifying scene as they left a Passover service this week: masked men on a sidewalk handing out leaflets demanding that Jews register and pay a fine or leave the area, witnesses said.

That the leaflets appeared in a highly uncertain political context did little to calm nerves or to dampen high-level international condemnation, including from Secretary of State John Kerry, who said Thursday in Geneva that “just in the last couple of days, notices were sent to Jews in one city indicating that they had to identify themselves as Jews.”

The leaflets were supposedly signed by Denis Pushilin, the leader of the Donetsk People’s Republic, the newly declared and unrecognized state that claims to represent ethnic Russians in eastern Ukraine. But that group and other pro-Russian groups quickly denied they had anything to do with them.

“This has nothing to do with us; it is a provocation,” said Alexander Maltsev, a spokesman for the People’s Republic, in a telephone interview. He said he did not know who was responsible, or their motives.