Dozens of protesters took over a building at Columbia University in New York early on Tuesday, barricading the entrances and unfurling a Palestinian flag out of a window in the latest escalation of demonstrations against the Israel-Hamas war that have spread to college campuses nationwide.

Video footage showed protesters on Columbia’s Manhattan campus locking arms in front of Hamilton Hall early on Tuesday and carrying furniture and metal barricades to the building.

Hamilton Hall is one of several buildings that were occupied during a 1968 civil rights and anti-Vietnam War protest on the campus.

Posts on an Instagram page for protest organisers urged people to protect the encampment and join them at Hamilton Hall where a “Free Palestine” banner hung from a window.

The student radio station, WKCR-FM, broadcast a play-by-play of the hall’s takeover, which occurred nearly 12 hours after Monday’s 2pm deadline for the protesters to leave an encampment of around 120 tents or face suspension.

Representatives for the university did not immediately respond to emails requesting comment but the Public Safety department said in a statement that access to the Morningside campus has been limited to students living in the residential buildings and employees who provide essential services, such as dining, public safety and maintenance staff.

There was just one access point into and out of campus.

“The safety of every single member of this community is paramount,” the advisory said.

Protesters said they planned to remain at the hall until the university conceded to the CUAD’s three demands: divestment, financial transparency and amnesty.

Universities across the US are grappling with how to clear out encampments as commencement ceremonies approach, with some continuing negotiations and others turning to force and ultimatums that have resulted in clashes with police.

Dozens of people were arrested on Monday during protests at universities in Texas, Utah, Virginia and New Jersey, while Columbia said hours before the takeover of Hamilton Hall that it had started suspending students.

Police moved to clear an encampment at Yale University in Connecticut on Tuesday morning, but there were no immediate reports of arrests.

The Yale Daily News, an independent student newspaper, reported that Yale and New Haven police surrounded the encampment in the Cross Campus quad with caution tape starting around 6am and said that anyone inside the blocked-off area would be subject to arrest and suspension if they did not leave.

Officer Christian Bruckhart, a New Haven police spokesperson, said no arrests had been made as of 7:30am.

At Princeton University, 13 people were arrested on Monday night including 11 students, after briefly occupying a building that houses its graduate school.

They received a summons for trespassing and have been barred from campus, President Christopher Eisgruber said in a statement.

The nationwide campus protests began as a response by some students to Israel’s offensive in Gaza after Hamas launched a deadly attack on southern Israel on October 7.

Militants killed around 1,200 people, most of them civilians, and took roughly 250 hostages.

Vowing to stamp out Hamas, Israel has killed more than 34,000 Palestinians in the Gaza Strip, according to the local health ministry.