New York City police enter Columbia University amid pro-Palestinian protests

New York City police officers entered the grounds of Columbia University on Tuesday night to arrest and disperse pro-Palestinian protesters who took over a campus building nearly 24 hours earlier and have occupied a tent camp at the Ivy League school for nearly two weeks.

Live television images showed helmeted police in tactical gear entering the elite campus in upper Manhattan, which has been the focal point of student protests that have spread to dozens of schools across the U.S. in recent days expressing opposition to Israel's war in Gaza.

"We're clearing it out," police officers yelled as they marched up to the barricaded entrance of Hamilton Hall, an academic building that protesters had broke into and seized control of in the early morning hours of Tuesday.

A long line of police officers were seen climbing into the building through a second-story window, using a vehicle with a ladder to gain access to the upper floor.

Dozens of other officers swarmed over the nearby protest encampment, as onlooking students standing just outside the campus jeered them with shouts of "Shame, shame!" Before long, officers were seen leading handcuffed protesters to police vehicles outside campus gates.

Police boarded about 50 detainees onto a bus, each of them with their hands bound behind their backs by zip ties, the entire scene illuminated with flashing red and blue lights of police vehicles. Ambulances and other emergency services vehicles stood at the read.

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

Columbia University officials earlier on Tuesday threatened academic expulsion of the students who seized Hamilton Hall.

The occupation began overnight when protesters broke