The Anti-Defamation League issued a security advisory to all Jewish institutions and synagogues in the wake of anti-Israel demonstrations around the globe protesting Israel’s military operation to stop rocket attacks from the Gaza Strip.

Fifty anti-Israel demonstrations have taken place in the US alone since the start a week ago of Operation Protective Edge. A number of the protests have seen incidents of violence, including in Los Angeles and Boston.

The ADL is encouraging heightened vigilance and recommending that institutions take steps to enhance their security and connect with law enforcement.

“The warning is in response to the violence and anti-Semitic expressions that we have seen at some of these demonstrations,” ADL spokesman Todd Gutnick told The Times of Israel on Monday.

“The tenor of some of these demonstrations has been extreme, with protesters chanting, ‘Death to Israel’ and other hateful messages and slogans,” he added.

Also on Monday, high-level US Department of Homeland Security officials spoke with Jewish leaders concerned about violence at rallies and demonstrations related to the recent conflict.

Two hundred Jewish community leaders participated in the conference call organized by the Secure Community Network, the security arm of national Jewish umbrella organizations.

DHS Deputy Secretary Alejandro Mayorkas and Deputy Assistant Secretary of Infrastructure Protection William Flynn were among the officials who addressed the leaders.

According to a SCN statement, the discussion focused on “security implications of operations in Gaza on Jewish communities both domestically and worldwide, and [a review of] security protocols for planned rallies and demonstrations in support of Israel.”

Pro-Israel demonstrators were assaulted this past week in Boston and Los Angeles.

Anti-Israel demonstrations in Europe have also turned violent.

On Sunday, at least three Jews were taken to the hospital in Paris after clashes erupted between anti-Israel protesters and young men guarding the Don Isaac Abravanel Synagogue in Paris, where worshipers were trapped for a short time. Two days earlier, a Molotov cocktail was thrown at a synagogue in a suburb of Paris.

In Berlin, several people were arrested after throwing rocks at police during a pro-Gaza rally over the weekend.

JTA contributed to this report.