Dozens of pro-Palestinian demonstrators at Columbia University have escalated their protest over the war in Gaza by occupying an academic building. Activists at the university in New York City seized Hamilton Hall early on Tuesday, barricading themselves inside. One student said the campus was "lawless", as officials grapple with the long-running demo which has prompted a wave of rallies elsewhere. Columbia has urged students and staff to stay away from campus on Tuesday. It earlier began suspending students who defied Monday's deadline of 14:00 EST (18:00 GMT) to leave their two-week encampment nearby. But as the deadline passed, dozens of students rallied at the site. Columbia Students for Justice in Palestine (SJP), one of the main protest groups, vowed to defy the order in a post on X, and called on activists to "protect the encampment". The group later announced the takeover of Hamilton Hall, highlighting that the venue was also the focus of student protests in 1968. Another group, Columbia University Apartheid Divest (CUAD), said it had "reclaimed" the building in honor of Hind Rajab, a six-year-old girl found dead in Gaza earlier this year. One student described the campus as "lawless, utter anarchy", with demonstrators breaking the building's windows to enter, before blocking the doors with furniture. Speaking to the BBC's US partner CBS News, Jessica Schwalb said the group had entered with "bags full of stuff", adding: "I'm guessing they're going to be living in there indefinitely." Demonstrations have rocked campuses across the US in recent weeks, sparked by New York police clearing an earlier encampment at Columbia. Hundreds of people have been arrested across the country — among them dozens of protesters at the University of Texas at Austin on Monday. Officials there said protesters had ignored directions to take down their tents and that "baseball-size rocks" had been found in the encampment. The UN human rights chief Volker Turk has voiced his concern that some law enforcement actions witnessed on American campuses have been "disproportionate in their impacts". "Freedom of expression and the right to peaceful assembly are fundamental to society," he added in a statement. At Virginia Commonwealth University (VCU) in Richmond, students said police used tear gas and pepper spray against their gathering on Monday. The university said the group had been "repeatedly" asked to leave, and echoed other institutions by saying many of those involved in the demonstration were not students. Elsewhere, there has been a rare agreement reached in Evanston, Illinois, between Northwestern University and protesters who have camped out for days in solidarity with the Palestinians. Under the deal, the university said it would permit "peaceful demonstrations", provided the encampment was limited to a single tent. Activists across the US are demanding that their universities, many with massive endowments, financially divest from Israel. Divestment means to sell or otherwise drop financial ties. Pressure has been building on the leadership of Columbia — an elite Ivy League university in Upper Manhattan —to act, or step aside. Posting on X before the occupation of Hamilton Hall, US House Speaker Mike Johnson labelled the scenes at Columbia an "utter disgrace" and called on the university's president to step down. Columbia's campus has become the focal point of the country's debate over the war in Gaza and US support for Israel, as well as fears that antisemitism is putting Jewish students in danger. Earlier on Monday, a group of House Democrats urged its board of trustees to resign if it could not "act decisively, disband the encampment, and ensure the safety and security of all of its students". Annual tuition and fees for Columbia add up to around $90,000 (£72,000) for undergraduates, making it one of the most expensive universities in the US. More than 100 people were arrested when police raided the earlier encampment on April 18. But activists redoubled their efforts, regrouping in another encampment and prompting university leadership to move to hybrid learning. A statement on Monday from Columbia's president, Dr. Minouche Shafik, reiterated that the university "will not divest from Israel", and that talks between academic leaders and student organizers had failed to result in an agreement. Several hours after the deadline passed for students to take down their camp — and before the break-in at Hamilton Hall was reported -—another official said the university had started to suspend students. This makes them ineligible to graduate. Officials say they want to avoid any disruption to graduation ceremonies on May 15. Another of the protesters' demands is amnesty for activists who face disciplinary action from the university. For now, the cluster of tents remains in place. Mahmoud Khalil, one of the students who has been negotiating with Columbia officials, told the BBC that protesters believed it was "highly probable" that police would again be called in again. "The students are here," added Khalil, who said he was a Palestinian refugee who grew up in Syria. "They are holding their ground." Many wore face coverings, telling the BBC they were worried about being recognized and facing recrimination. But the university wrote in its letter on Monday that it had already identified several participants. The BBC is tracking protests or encampments on campuses in at least 22 other states and Washington DC. They have also been reported in Canada, France and Australia. Jewish students on numerous campuses have voiced concern about their safety, amid alleged incidents of harassment and threats of violence by some protests participants, The White House is walking an increasingly fine line over the campus protests, seeking to balance the right to peaceful protest with condemnation of hate speech. "It is a painful moment, we get that," press secretary Karine Jean-Pierre said. Declining to say how university leadership should act, she added: "Free expression has to be done within the law." Republicans, including former President Donald Trump, have also highlighted antisemitic chants and incidents at the protests. — BBC