Dozens of protesters took over a building at Columbia University in New York early on Tuesday as the university began suspending student protesters who defied a deadline to vacate their encampment on the campus.

Video footage showed the students barricading the university entrances and unfurling a Palestinian flag out of a window in the latest escalation of demonstrations against the Israel-Hamas conflict.

Protesters on Columbia's Manhattan campus locked arms in front of Hamilton Hall, carrying furniture and metal barricades to the building, one of several that was occupied during a 1968 civil rights and anti-Vietnam War protest on the campus.

Posts on an Instagram page for protest organizers shortly after midnight urged people to protect the encampment and join them at Hamilton Hall.

The university had given students until 2 pm Monday to clear out the encampment, warning that they would face immediate suspension "pending further investigation" and be barred from completing the spring semester if they didn't leave by then.

The university said it had identified some but not all students at the encampment. The students were likely to be notified by email of their suspensions, which are expected to cut off their access to school buildings and amenities and potentially keep them from taking finals.

The activists had defied the deadline with chants, clapping and drumming, with hundreds of pro-Palestinian demonstrators marching around the encampment.

Columbia University faculty members stood at the entry of the encampment on the campus, holding hands to protect students they said were exercising freedom of speech. Police were outside the encampment at the school gates as protesters there chanted.

But by 4 pm most of the protesters had begun to disperse, leaving only what appeared to be several dozen students and about 80 tents inside the encampment.

"These repulsive scare tactics mean nothing compared to the deaths of over 34,000 Palestinians," said a statement, read out by a student at a news conference after the deadline, referring to the death toll in Gaza.

"We will not move until Columbia meets our demands or … are moved by force," said the student, who would not give his name.

The campus was thronged with media as the deadline approached, but there was no police presence near the encampment.

"Today, they are maligning us. It's shortsighted and it's unfair," Sueda Polat, a 23-year-old graduate student and one of the student organizers, told China Daily.

"They are really kind of fanning the flames," Jamil Mohamad, a 32-year-old Middle Eastern studies student, told China Daily.

The demonstrators are demanding that Columbia divest its $13.6 billion endowment from any company linked to Israel. That includes companies like Microsoft and Airbnb that do business in Israel.

Primary demand

"Our primary demand is financial divestment, and that means calling for Columbia University to pull its investments away from companies that are supporting the Israeli apartheid system or companies that are directly profiting from the genocide of Gaza and the system of Israeli apartheid," Althea C., a member of the "Jews for Ceasefire" organization at Columbia, told China Daily.

But the university said Monday that it wouldn't divest from Israel.

It offered to create an expedited timeline for a review of new proposals from students by the school's Advisory Committee for Socially Responsible Investing, which explores divestment, said Columbia President Minouche Shafik.

The number of protesters arrested on more than 20 campuses across at least 16 states has approached 1,000.

Meanwhile, at the University of Texas at Austin, police clashed with protesters Monday, including using pepper spray, and made arrests while dismantling an encampment, adding to the more than 350 people detained nationwide over the weekend.

"No encampments will be allowed," Texas Governor Greg Abbott said on social media.

Agencies contributed to this story.