Protesters detained as police head for Hamilton Hall, which students began occupying on Tuesday morning, and the main campsite.

Large numbers of New York City police officers have entered the campus of Columbia University in the latest escalation in the Gaza protests that have swept dozens of universities, mostly in the United States.

The New York Police Department received a notice from Columbia authorising officers to take action shortly before they entered the campus late on Tuesday night, a law enforcement official who spoke on condition of anonymity told The Associated Press news agency.

Live television images showed police entering the campus in upper Manhattan, which has been the focal point of student protests against Israel’s war in Gaza, in which more than 34,535 Palestinians have been killed.

After entering the campus, some officers approached Hamilton Hall, the administration building that students began occupying early on Tuesday morning after the management said it had begun suspending students who had refused to meet a deadline to disperse on Monday.

They renamed the building “Hind’s Hall”, in memory of six-year-old Palestinian girl Hind Rajab who was killed in Gaza in February.

“We’re clearing it out,” police in a riot unit yelled as they marched up to the barricaded entrance to the building. Dozens more police marched to the protest encampment.

Columbia Students for Justice in Palestine said in a post on X that the police officers were “wearing riot gear” and that “multiple blocks have been barricaded off”.

A long line of police officers were seen climbing into the building from the top of a truck into a second-storey window. Dozens of other officers targeted the nearby protest encampment.

Shortly afterwards, officers were seen leading protesters, their hands tied behind their backs with plastic zip ties, to police vehicles outside the campus gates.

“Free, free, free Palestine,” chanted protesters outside the building. Others yelled “Let the students go”.

‘They’re students’

Dozens of protesters barricaded the entrances of Hamilton Hall after occupying Hamilton Hall on Tuesday.  A student organiser who spoke to Al Jazeera said that the occupation group was separate from the group that had established a camp on the campus lawn.

At an evening news briefing held a few hours before police entered the campus, Mayor Eric Adams and city police officials alleged the Hamilton Hall takeover had been instigated by “outside agitators” who lacked any affiliation with Columbia and were known to law enforcement for provoking lawlessness.

Adams suggested some of the student protesters were not fully aware of “external actors” in their midst.

“We cannot and will not allow what should be a peaceful gathering to turn into a violent spectacle that serves no purpose. We cannot wait until this situation becomes even more serious. This must end now,” the mayor said.

One of the student leaders of the protest, Mahmoud Khalil, a Palestinian student at Columbia’s School of International and Public Affairs, disputed the claims.

“They’re students,” he told the Reuters news agency.

The protesters are calling for the university to sell off any investments linked to Israel, be transparent about its financial ties to the country, and provide amnesty from any disciplinary measures to all students participating in the rallies.

Universities across the US are grappling with growing protests at the same time as they prepare for end-of-year graduation ceremonies.

On Tuesday, police also fired tear gas at students who set up a Gaza solidarity camp at the University of Southern Florida in Tampa, according to videos from journalists and witnesses verified by Al Jazeera.

The videos also show police forces arresting two people at the protest scene.