Student demonstrators at Columbia University have defied an ultimatum to disperse or face immediate suspension, as tensions rose at the epicentre of pro-Palestinian protests that have erupted at US colleges.Police arrested around 275 people on four separate campuses across the United States over the weekend, with the White House calling on the demonstrations to remain peaceful.Authorities at Columbia in New York issued a statement on Monday saying that the protesters’ encampment must be cleared, and adding that the university would not divest financial holdings linked to Israel – a key demand of demonstrators.However, student protesters pushed back, vowing to defend their camp on the prestigious institution’s main lawn, despite threats of suspensions and disciplinary action after a 2pm (1800 GMT) deadline.Protests against the Gaza war, with its high civilian death toll of Palestinians, have posed a challenge to university administrators trying to balance free speech rights with complaints that the rallies have veered into anti-Semitism and hate speech.For almost two weeks now a wave of protests against Israel’s war in Gaza has swept through US university campuses from coast to coast, after around 100 protesters were arrested at Columbia on April 18.Footage of police in riot gear summoned at various colleges to break up rallies have been viewed around the world, recalling the protest movement that erupted during the Vietnam war.At University of California, Los Angeles skirmishes broke out on Sunday between pro-Palestinian protesters and supporters of Israel.Columbia University president Minouche Shafik, in her statement announcing talks had broken down, said that “many of our Jewish students, and other students as well, have found the atmosphere intolerable in recent weeks. Many have left campus, and that is a tragedy”.“Anti-Semitic language and actions are unacceptable and calls for violence are simply abhorrent,” she said. “One group’s rights to express their views cannot come at the expense of another group’s right to speak, teach, and learn.”Protest organisers deny accusations of anti-Semitism, arguing that their actions are aimed at the Israeli government and its prosecution of the conflict in Gaza.They also insist some incidents have been engineered by non-student agitators.Columbia classics professor Joseph Howley told AFP that the school’s statement amounted to yielding to outside political pressure.He said Columbia is “affirming the false premise that the mere presence of political speech on behalf of Palestine is a threat to Jews like myself”.He called such a position “absurd and dangerous”.The Gaza war started following the events of October 7 that left around 1,170 people dead, according to an AFP tally of Israeli official figures.Palestinian militants also took roughly 250 people hostage.Israel estimates 129 hostages remain in Gaza, including 34 the military says are dead.Israel’s retaliatory offensive has killed almost 34,500 people in Gaza, mostly women and children, according to the Hamas-run territory’s health ministry.