Kerry acknowledged the reports during a press conference in Geneva, where he announced that U.S., Russian, Ukrainian and European Union negotiators had agreed on a series of measures to de-escalate the standoff between Kiev and Moscow.
“Just in the last couple of days, notices were sent to Jews in one city indicating that they had to identify themselves as Jews," said Kerry.
“This is not just intolerable; it's grotesque, is beyond unacceptable,” he added. “And 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, and unanimously every party today joined in this condemnation of that kind of behavior.”
Reports on Thursday said that Jews in the Ukrainian city of Donetsk, where pro-Russian militias have seized control of buildings and neighborhoods, were given leaflets ordering them to register with separatist groups. According to a report, the pro-Russian group identified on the leaflets though denied involvement.
The reports sparked condemnation on Capitol Hill, with lawmakers urging the Obama administration to take steps to protect Jewish citizens in Ukraine.
Rep. Nita Lowey, D-N.Y., in a letter to Kerry on Thursday called the reports “an unacceptable escalation of the crisis in Ukraine and cause for both grave concern and immediate action.”
“As you are well aware, the singling out of Jewish communities for further scrutiny and possible punishment reeks of age-old anti-Semitic policies,” she said.
“All of the parties involved in the ongoing crisis in Ukraine must understand in no uncertain terms that the world community will not tolerate such contemptible and atrocious behavior,” Lowey added. “I urge you to do everything possible to ensure that Jewish and other minority communities throughout the country are protected from any form of prejudice.”
Following Russia's annexation of Ukraine's Crimea region, a number of pro-Russian groups in eastern Ukraine are calling for greater autonomy from Kiev.
Russia has said it has no intention of invading Ukraine further but has massed troops on the border and is reserving the right to intervene to protect ethnic Russians in the neighboring country.
Kerry said the diplomatic deal announced on Thursday was only “preliminary” and cautioned that the U.S. would watch closely to ensure that both Ukraine and Russia honored their agreements.
White House correspondent Susan Crabtree contributed to this report.