Trump says pro-Palestinian campus protester 'first arrest of many to come'

US President Donald Trump said Monday that the detention of a leader of pro-Palestinian protests at Columbia University in New York is "the first arrest of many to come."

"We know there are more students at Columbia and other Universities across the Country who have engaged in pro-terrorist, anti-Semitic, anti-American activity, and the Trump Administration will not tolerate it," Trump wrote on his Truth Social platform.

Mahmoud Khalil, one of the most prominent faces of the university's protest movement that erupted last year in opposition to Israel's war in Gaza, was arrested by immigration officials over the weekend.

The Department of Homeland Security said the action was taken "in support of President Trump's executive orders prohibiting anti-Semitism, and in coordination with the Department of State."

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Khalil, a Columbia graduate, held a permanent residency green card at the time of his arrest, according to the Student Workers of Columbia union.

Trump threatened in his post further action against other campus protesters, some of whom he alleged without evidence to be "paid agitators."

"We will find, apprehend, and deport these terrorist sympathizers from our country -- never to return again," he wrote.

The American Civil Liberties Union (ACLU) condemned Khalil's arrest, calling it "unprecedented, illegal, and un-American."

"The government's actions are obviously intended to intimidate and chill speech on one side of a public debate," said Ben Wizner, director of the ACLU's Speech, Privacy and Technology Project, in a statement.

The arrest also prompted an outcry from the United Nations, with the spokesman for UN Secretary-General Antonio Guterres saying Monday "it is crucial to underscore the importance of respecting the right of freedom of expression and the right to peaceful assembly everywhere."

US campuses including Columbia's were rocked by student protests against Israel's war in Gaza following the October 7, 2023 Hamas attack. The demonstrations ignited accusations of anti-Semitism.

Protests -- some of which turned violent and saw campus buildings occupied and lectures disrupted -- pitted students protesting Israel's conduct against pro-Israel campaigners, many of whom were Jewish.