The FBI says it has received “credible information of a broad threat” to synagogues in the US state of New Jersey.
“We ask at this time that you take all security precautions to protect your community and facility,” said the agency.
It is not clear whether the threat is focused on a particular area of New Jersey, or statewide.
Last year, a record 2,717 anti-Semitic incidents were reported in the US.
It was the highest number since the Anti-Defamation League (ADL), an anti-hate monitoring group, began counting such incidents in 1979.