MAJDI FATHI/AFP via Getty Images
- Jewish institutions in the US are on guard following Hamas' surprise attack on Israel.
- The Jewish Federations of North America said there are currently no known "credible threats."
- But it is urging Jewish groups to review their security procedures and stay in touch with police.
The attack on Israel launched early Saturday morning by Hamas militants in Gaza has shocked Jewish organizations and prompted concerns of anti-Semitic attacks in the United States and elsewhere.