RUTHFULLY YOURS

The U.K. has seen a rising tide of antisemitic threats since the attacks last Saturday, and children from several Jewish schools in London were told to stay home Friday. Australian officials apologized to the Jewish community after chants of “Gas the Jews” broke out at a pro-Palestinian protest there last weekend.

In China on Friday, a 50-year-old Israeli man who works at Israel’s embassy was stabbed in broad daylight on the streets of Beijing. Chinese police said they were investigating the attack, and it wasn’t clear if it was related to events in the Middle East.

In the U.S., some parents fretted about sending their children to school Friday as police stepped up their presence. A bomb threat over social media prompted a congregation to evacuate a Chicago-area synagogue.

“Every Jewish institution is on high alert,” said Rabbi David Ingber, the founding rabbi of Romemu, a synagogue in Brooklyn and Manhattan’s Upper West Side, in New York City. Both locations were still open Friday but with heightened security. “Our number one responsibility is to protect our people at this moment,” Ingber said.

President Biden has called the Hamas attack the deadliest day for Jews since the Holocaust. Israel’s military has responded with a military campaign aimed at dismantling Hamas, a group the U.S., Israel and others have designated a terrorist organization.

“When antisemitism runs rampant in Israel, ultimately, it affects Jews all over the world. And even in America, there’s no exception,” said Rabbi Shaanan Gelman, of a synagogue in Skokie, Ill.

Synagogue leaders decided to evacuate the facility this week after a bomb threat circulated among high-school students on Snapchat, Gelman said. Nothing came of it.

“When former officials from Hamas publicly declare a day of rage and antisemitism and attacking Jews, of course we’re going to be frightened because we’ve seen this film play out many times in history before,” said Gelman, who has family members living in Israel. “But our response is absolutely not to cower.…We’re not going to be afraid to worship in our own way.”

The Jewish Federations of North America, a philanthropy that represents nearly 400 independent Jewish communities, sent a memo to its local affiliates Thursday advising them they could remain open. “We don’t want to shut down our community,” said Eric Fingerhut, the chief executive.

Marc Schiller, who attends a synagogue in Manhattan’s Upper West Side, said he would go to Friday’s service.

“I take my lead and motivation from my brothers and sisters in Israel,” said Schiller, whose father was a Holocaust survivor. “People are seeking community and connection to others.”

Still, some had second thoughts. A couple of Israeli musicians canceled their participation for Friday service at the New Shul in Manhattan because they didn’t want to be included in any big Jewish gatherings, said Rabbi Misha Shulman.

“Some people want to go out into the streets and proudly say ‘I’m Jewish,’ and other people have all kinds of trauma scenarios going on in their heads,” Shulman said.

Some parents grappled with whether to send their children to school on Friday. Jennifer Ludmir, 34, said all three of her children went to their Jewish school in Houston. The family also planned on going to the synagogue Friday night.

“My husband and I feel very strongly that we cannot and should not cower in the face of terror,” Ludmir said.

Police in metro areas including Chicago and St. Louis said they weren’t aware of specific threats but had increased patrols around synagogues and mosques.

Islamic institutions were on guard, too, and Muslims in the Middle East rallied in support of the Palestinians. In Massachusetts, someone spray-painted the word “Nazis” on the sign for the Palestinian Cultural Center for Peace and the Islamic Seminary of Boston earlier in the week. Gov. Maura Healey, a Democrat, called the defacement “sickening.”

“We’re talking about a space dedicated to peace, faith and community,” she said on X, formerly known as Twitter. “Hate will not be tolerated in Massachusetts.”

A Boston Police spokesman said there have been no arrests and the investigation remains active.

Police in London, which has one of Europe’s largest Jewish populations and a large Muslim community, said that thousands of officers were being drafted for extra patrols.

London police had tallied 105 reports of antisemitic incidents, compared with 14 such incidents over the same period last year, a spokesperson said. During the same period, there have been 58 anti-Muslim incidents, up from 31 anti-Muslim incidents last year.

Trevor Stern, an American master’s student at Oxford University and president of the Oxford Jewish Society, said that on Wednesday night, he and his roommate decided to put a mezuzah—a rolled scroll with verses—on his door frame.

“In light of rising antisemitism around the world, we had agreed that the best thing to do would be to publicly display and reaffirm Jewish identity,” he wrote in a column in the Times of London. The next morning, when he left his apartment, the mezuzah had been ripped off and stuck upside down on the front door to the building.

“It left me feeling quite shaken,” he wrote. “This was a case of antisemitic harassment by someone in the building.”

Three Jewish schools in North London told students to stay home Friday after Hamas called for a global “Day of Rage” in support of Palestinians. Some Jewish schools told their pupils to not wear their jackets to school in order not to identify themselves as Jewish and boys told to hide their skull caps, often called a kippah or yarmulke, with baseball caps.

Ilai Schechter, a 30-year-old management consultant, was traveling for work in Edinburgh this week when he came across a small group of protesters waving Palestinian flags. He covered up his kippah.

“It’s the first time in my adult life that I have hidden my Jewishness by covering up my kippah in public,” he said.

Julie Steinberg and Alistair MacDonald contributed to this article.

Write to David Luhnow at david.luhnow@wsj.com, Shannon Najmabadi at shannon.najmabadi@wsj.com, Joseph De Avila at joseph.deavila@wsj.com, Adolfo Flores at adolfo.flores@wsj.com and Jon Kamp at Jon.Kamp@wsj.com