Two Israeli embassy staffers were shot dead late Wednesday outside a Jewish museum in Washington by a gunman who shouted "free Palestine," authorities said, with US and Israeli leaders expressing outrage over the killings.

President Donald Trump condemned the attack in the heart of the US capital, saying "These horrible D.C. killings, based obviously on antisemitism, must end, NOW!"

"Hatred and Radicalism have no place in the USA," he added on social media.

Shots rang out on the sidewalk outside the Capital Jewish Museum in Washington as the venue held a social event for young professionals and diplomatic staff.

The victims were a young couple who planned to get married, the Israeli ambassador said.

A video clip circulating on social media showed a young bearded man in a jacket and white shirt shouting "free, free Palestine" as he was led away by police.

Police confirmed the suspected shooter walked into the museum after the attack and had been detained.

"The shooting was committed by a single suspect who is now in custody," Washington Police Chief Pamela Smith told reporters.

"Prior to the shooting, the suspect was observed pacing back and forth outside of the museum. He approached a group of four people, produced a handgun and opened fire.

"After the shooting, the suspect then entered the museum and was detained by event security."

She said the handcuffed man -- whom she named as Elias Rodriguez, 30, from Chicago -- identified where he had discarded the gun.

'Despicable antisemitic murderer'

"We are witnessing the terrible price of antisemitism and the wild incitement against the State of Israel," Israeli Prime Minister Benjamin Netanyahu said in a statement, announcing extra security arrangements at Israeli missions around the world.

"Blood libels against Israel are paid in blood -- and they must be fought relentlessly," he said.

"My heart aches for the families of the beloved young man and woman, whose lives were abruptly cut short by a despicable antisemitic murderer."

The targeted event was an annual reception hosted by the American Jewish Committee (AJC) for young Jewish professionals and the Washington diplomatic community.

The evening was "dedicated to fostering unity and celebrating Jewish heritage," with an invitation to the event saying the location would be "shared upon registration."

"We are devastated that two cherished friends and partners from the Israeli embassy were shot and killed as they left an American Jewish Committee event," AJC CEO Ted Deutch said in a statement.

"It strongly appears that this was an attack motivated by hate against the Jewish people and the Jewish state. This senseless hate and violence must stop."

The museum is in downtown Washington, close to the US Capitol and just over one mile (1.6 kilometers) from the White House.

Police Chief Smith said officers responded to multiple calls of a shooting near the museum at around 9:00 PM on Wednesday (0100 GMT Thursday). 

First responders found a man and a woman unconscious and not breathing. Despite life-saving efforts, both were pronounced dead.

Young couple

Israel's Ambassador to the United States Yechiel Leiter told reporters the young staffers were a couple about to get engaged. 

"The young man purchased a ring this week with the intention of proposing to his girlfriend next week in Jerusalem," Leiter said.

"They were a beautiful couple."

He added that he spoke to Trump by telephone, with the president assuring him that the United States will "do everything it can possibly do to fight and end anti-Semitism."

"We'll stand together tall and firm, and we will confront this moral depravity without fear and with determination," Leiter said.

Emergency vehicles remained at the scene in the early hours of Thursday after police taped off the area.

"We're going to stand together as a community in the coming days and weeks to send the clear message that we will not tolerate anti-Semitism," Washington Mayor Muriel Bowser told reporters.

"The horrific incident is going to frighten a lot of people in our city, and in our country. I want to be clear that we will not tolerate this violence or hate."

More reactions pour in

On X, Israel's president Isaac Herzog condemned the shooting, calling it (via X's automatic translation) "despicable" and a "heinous act of terror driven by antisemitism."

He also called upon public figures in Israel to "understand the magnitude of responsibility at this hour."