A group of neo-Nazis attacked the tomb of revered spiritual leader Rabbi Nachman of Breslov in the Ukraine, defiling the gravesite with fake blood and the head of a pig and physically assaulting Jewish worshipers with tear gas overnight on Tuesday.

Two Israeli nationals were taken to a hospital for treatment following the attack, which took place at around 2 AM on Wednesday morning in the city of Uman.

ISRAEL: Anti Semitic attack on Rebbi Nachmans Kever in UMAN , they put red juice and a pigs head all over the Taino pic.twitter.com/WJdk3ScXPh

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Rabbi Nachman, a very significant Jewish figure who founded the Hasidic movement, is buried in Uman. His grave is a popular pilgrimage site for religious Jews, drawing thousands of visitors during the Jewish New Year.

Rabbi Yisrael Elhadad, the sexton of the synagogue located on the tomb site, described the two attackers as neo-Nazis. The men entered the synagogue’s main hall with bottles of paint and sprayed tear gas at the five or six Jewish worshipers there, he told Ynet News.

While the blood was fake, the pig’s head, which had a swastika carved into it, was real. As pigs are considered an unclean animal, a pig’s head in a synagogue is a serious desecration.

Religious Jews who arrived in the morning for prayers were greeted by the gruesome scene.

Israeli leaders swiftly condemned the “barbaric” attack and called for a quick response from Ukrainian authorities.

“I was shocked to the very core to hear of the terrible and barbaric desecration that was done last night at the holy site of Rabbi Nachman from Breslov,” Interior Minister Aryeh Deri said on Wednesday.

“The event last night had echoes of the darkest days of the Jewish people’s history in Europe,” MK Yair Lapid wrote in a letter to Israel’s Ukrainian envoy. “Today, we look to your government to immediately condemn this act and use all the power at your disposal to find the perpetrators and bring them swiftly to justice.”