Police beefed up security at schools and religious buildings across Washington Friday as the US capital reeled from the fatal shooting of two Israeli embassy staffers outside a Jewish museum.

The 31-year-old Chicago man accused of Wednesday's attack shouted "Free Palestine" as he was taken away by police -- exacerbating fears over rising anti-Semitism since Israel's invasion of Gaza following the unprecedented October 2023 Hamas attack.

"Around DC, you will see an increased presence of law enforcement officers around the community, you will find us around our faith-based organizations," Metropolitan Police (MPD) Chief Pamela Smith told reporters.

"You will see an increased presence around our schools and places like the DC Jewish Community Center. We stand shoulder to shoulder with our Jewish community."

Authorities in Washington said they were investigating the shooting "as an act of terrorism and as a hate crime" ahead of a preliminary court hearing set for alleged killer Elias Rodriguez on June 18.

President Donald Trump -- who spoke with Israel's Prime Minister Benjamin Netanyahu -- posted on social media that the attack was clearly anti-Semitic.

The shooting, just a mile (1.6 kilometers) from the White House, triggered international outrage as Israel blamed European criticism of its Gaza offensive, which came in response to the Hamas attack.

The victims of Wednesday's attack, Israeli citizen Yaron Lischinsky and American Sarah Lynn Milgrim, had been planning to marry.

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Washington Mayor Muriel Bowser gathered her interfaith council, local Jewish leaders, city councillors and law enforcement officials on Thursday to coordinate the community response.

"We have a long history, and a lot of practice in our city, of working with Jewish organizations around safety and around protection," she told a news conference.

Aaron Hiller, head of the board of the Hill Havurah synagogue, who was organizing a vigil for the victims in Washington late Friday, said the attack was "unfortunately ... not unexpected."

"Both acts of anti-Semitism and acts of violence are all too common," Hiller said, though insisting the community was "very safe."

"I walk to work and from work very late at night (and) my kids roam the neighborhood freely," he said.

But "particularly since the events of October 7th, we are taking steps to enhance our security here and elsewhere."

Daniel Ben Chitrit, who was at the vigil, said he was deeply shaken by Wednesday's killings, adding that he was supposed to have been at the Jewish Museum that evening.

"I didn't know the victims, but I've met the victims at previous events," he said.

He insisted there had been no way for the shooter to know the couple worked at the Israeli embassy.

"All he knew is that they were coming from the Jewish event," he said.