U.S. Attorney General Jeff Sessions said on Monday that recent bomb threats against Jewish groups are “unacceptable”.
Speaking to reporters, Sessions called the threats a “very serious and destructive practice”.
Earlier on Monday, at least 10 Jewish community centers and Jewish day schools across the United States received bomb threats, the fifth wave of such threats in less than two months.
Paul Goldenberg, director of the Secure Community Network (SCN), told JTA shortly after reports of the bomb threats began coming in that his organization was working closely with the Department of Homeland Security and the FBI to identify the perpetrators and stop the threats.
SCN is an affiliate of the Jewish Federations of North America that advises Jewish groups and institutions on security.
Some 60 JCCs and Jewish schools have received nearly 70 bomb threats since Jan. 9, forcing the evacuation of hundreds, including preschool children, from the buildings.
Two Jewish cemeteries have been vandalized in recent weeks. Nearly 200 headstones were knocked over in a Jewish cemetery in St. Louis.
In another incident, dozens of headstones were toppled in a Jewish cemetery in Philadelphia.
White House press secretary Sean Spicer told reporters on Monday that President Donald Trump is "deeply disappointed and concerned" by recent anti-Semitic incidents.
"The President remains deeply disappointed and concerned by the reports of further vandalism at Jewish cemeteries," Spicer said.
"The cowardly destruction in Philadelphia this weekend comes on top of similar accounts from Missouri and threats made to Jewish community centers around the country.
"The President continues to condemn these and any other form of anti-Semitic or hateful acts in the strongest terms,” he added.