Ukrainian police detained dozens of people protesting what they called an uncontrolled influx of Jewish pilgrims, police and the Svoboda nationalist party said.
Some 100 people attended the protest in Uman, the site of an annual pilgrimage by tens of thousands of Hasidic Jews who visit the grave of a prominent Jewish cleric, Rebbe Nachman of Breslov.
Svoboda held the rally to demand stricter legal and sanitary controls on pilgrims. Its activists say the pilgrim influx must be better regulated, and presents a security and health risk.
"We are not anti-Semites, we do not have anything against Jews," said Tetyana Chornomaz, head of the local Svoboda branch. But "we have many questions regarding their stay in Ukraine."
Chornomaz said riot police detained about 20 people following brief scuffles after the rally on Sunday, but it was not clear whether they faced any charges.
The Interior Ministry said about 60 people were detained, Interfax reported.
The rally took place days before the 70th anniversary of the Babi Yar massacre, the mass killing of Jews by Nazis after the occupation of Kiev in 1941.