Police in New York City arrested dozens of pro-Palestinian demonstrators holed-up in an academic building on Columbia University campus.

Officers removed a protest encampment that the Ivy League school had sought to dismantle for nearly two weeks, saying they had "no choice" but to do so.

The organisers of the event said the students did not pose a danger and called on police to back down.

Police were seen loading dozens of detainees onto a bus, each with their hands bound behind their backs by zip-ties, the entire scene illuminated with flashing red and blue lights of police vehicles.

Soon after, a long line of officers climbed into Hamilton Hall, an academic building that protesters had broken into and occupied.

Police entered through a second-story window, using a police vehicle equipped with a ladder.

Spokesperson for the University Ben Chang said the demonstrators "have chosen to escalate the situation through their actions.

“After the University learned overnight that Hamilton Hall had been occupied, vandalised, and blockaded, we were left with no choice."

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Columbia University Apartheid Divest, the coalition of student groups that has organised the protests, were seeking three demands from the faculty.

These were divestment from companies supporting Israel's government, greater transparency in university finances, and amnesty for students and faculty disciplined over the protests.

At an evening news briefing held a few hours before police entered Columbia, Mayor Eric Adams and city police officials said the Hamilton Hall takeover was instigated by "outside agitators" who lack any affiliation with Columbia and are known to law enforcement for provoking lawlessness.

Police said they based their conclusions in part on escalating tactics in the occupation, including vandalism, use of barricades to block entrances and destruction of security cameras.

The university also released a letter from Baroness Shafik, the university’s president, to the NYPD requesting assistance earlier in the day.

She wrote: “Columbia is committed to allowing members of our community to engage in political expression – within established rules and with respect for the safety of all.

"The policies we have in place around demonstrations are in place to support both the right to expression and the safety and functioning of our University."

She requested that police stay on campus until at least May 17, two days after graduation, "to maintain order and ensure that encampments are not re-established."

Sueda Polat, one of the student negotiators for Columbia University Apartheid Divest, said: "Columbia will be proud of these students in five years."

There have been other protests across other US campuses, with students at Northeastern University in Boston and University of Southern California holding similar demonstrations.

White House spokesperson John Kirby on Tuesday called the occupation of campus buildings "the wrong approach."