“When we arrived we encountered multiple victims ... with injuries consistent with burns and other injuries,” Redfearn said.

A large area of the Boulder pedestrian shopping district has been closed off, with businesses closed. People have been asked to avoid the area, which Redfearn said was “not safe yet”, as police were also dealing with a vehicle of interest. Officers were wearing bomb suits.

University student Brooke Coffman said she saw four women lying or sitting on the ground with burns on their legs after the attack. One of them appeared to have been badly burnt on most of her body and had been wrapped in a flag by someone, she said.

She described seeing a man whom she presumed to be the attacker standing in the courtyard shirtless, holding a glass bottle of clear liquid and shouting.

“Everybody is yelling, ‘Get water, get water,’” Coffman said.

Senate Minority Leader Chuck Schumer, a prominent Jewish Democrat, said he was closely monitoring the situation.

“This is horrifying, and this cannot continue. We must stand up to antisemitism.”

Colorado Governor Jared Polis said he was “closely monitoring” the situation, adding that “hate-filled acts of any kind are unacceptable”.

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The attack comes just weeks after a Chicago-born man was arrested over the fatal shooting of two Israeli embassy employees in Washington, DC, after an event hosted by the American Jewish Committee, an advocacy group that fights antisemitism and supports Israel.

The shooting has fuelled polarisation in the United States over the war in Gaza between supporters of Israel and pro-Palestinian demonstrators.

More to come

Reuters, AP