The slaying of two Israeli Embassy aides on Wednesday outside a Jewish museum in Washington was an extreme example of what law enforcement officials and others call a global surge in antisemitic incidents that emerged after Hamas terrorists killed more than 1,200 people and seized 250 hostages on Oct. 7, 2023.

Across the world, offenses against Jewish people and property have doubled or even tripled since the Hamas attacks and have remained at historically high levels as Israel has waged a 19-month bombing campaign and aid blockade that the Gaza Health Ministry says has killed more than 50,000 Palestinians.

Groups that monitor hate crimes around the world said the Hamas attack and the subsequent war had helped fuel tens of thousands of incidents, including cases of verbal abuse, a torrent of online attacks on social media, Nazi-themed vandalism, personal threats and violent attacks resulting in injury and death.

“Everywhere across the board, you had more incidents than before Oct. 7 — that impression is lasting,” said Professor Uriya Shavit, the director of the Religious Studies Program at Tel Aviv University, which produces one of the most comprehensive annual reports on the level of antisemitism worldwide.

Professor Shavit and others said it could be difficult to clearly define what qualifies as an antisemitic incident at a time of heightened political outrage around the world, especially about the humanitarian impact of Israel’s conduct in the war. The complexity of the issue was underscored during the 2024 protests at universities in the United States, where administrators and police officers struggled to confront both legitimate political expression and abusive or hateful incidents.

Despite the intensity of feelings about the conflict, most of the cases of reported antisemitism around the globe fall far short of the kind of extreme violence that erupted on Wednesday outside the Capital Jewish Museum, where the American Jewish Committee was hosting a reception for young diplomats in Washington.