Columbia University, the epicenter of U.S. student protests against the war in Gaza, on Monday cancelled its main graduation ceremony, as colleges seek to contain the demonstrations that have rocked campuses for weeks.

The Ivy League school in New York, where at least 100 pro-Palestinian protesters were arrested last week, cited security concerns as it canceled the ceremony scheduled for May 15, with smaller events planned instead.

"We will focus our resources on those school ceremonies and on keeping them safe, respectful, and running smoothly," Columbia said in a statement.

Graduation ceremonies -- a key event in American university life -- have become a new target for pro-Palestinian demonstrators after heavy-handed policing removed many of their on-campus encampments.

On Saturday, dozens of pro-Palestinian protesters wearing graduation gowns and keffiyehs briefly interrupted a commencement ceremony at the University of Michigan.

Some unfurled Palestinian flags and marched toward the stage chanting "You are funding genocide," before being stopped by police.

Others in the audience held Israeli flags, and a plane was seen flying overhead carrying a banner that said: "We stand with Israel. Jewish Lives Matter."

At Northeastern University in Boston, a man wearing a shirt splattered with fake blood approached the stage before being detained by police on Sunday.

The University of Southern California in April canceled its main graduation ceremony fixed for May 10 following pro-Palestinian protests on campus, citing a need for additional safety measures at the event that normally hosts 65,000 people.

Widespread protests

Police have taken tougher measures on pro-Palestinian protests in the past week, with some university presidents explicitly requesting law enforcement support.

Columbia's president Minouche Shafik faced criticism for calling in police to clear protesters who had barricaded themselves inside a university building.

Dramatic scenes followed, with helmet-clad officers marching handcuffed demonstrators out of the university grounds onto police buses.

Columbia, one of America's most elite universities, was among the first to mobilize against Israel's war in Gaza in protests that spread across the United States, with police arresting more than 2,000 people nationwide.

On Saturday, riot police were filmed breaking up a pro-Palestinian encampment at the University of Virginia in Charlottesville, where at least 25 people were arrested.

Police also moved Monday to clear a demonstration at the University of California, San Diego, with TV images showing protesters facing off with officers behind steel barriers.

Its sister institution in Los Angeles, UCLA, said it had on Monday reinstated in-person classes which were moved online after demonstrators took over the campus with tents and banners, before being cleared by police in confrontations during the weekend.

'Order must prevail'

For many students who graduated from high school during the Covid pandemic, it will be the second such ceremony that is canceled due to external disruption.

President Joe Biden said on Thursday that "order must prevail" on US campuses, adding that protests should not be allowed to disrupt classes and graduations.

The protests have strained relations between the United States and its key ally Israel, which has been at war in Gaza since October.

Israel's President Isaac Herzog condemned the protests, saying on Thursday that US campuses were "contaminated by hatred and anti-Semitism."

Meanwhile, Donald Trump -- Biden's competitor in November's presidential election -- has accused him of being soft by failing to condemn the pro-Palestinian supporters.

Trump referred to protesters at Columbia as "raging lunatics and Hamas sympathizers" and called on college presidents to "take back our campuses."

© Agence France-Presse