Police have made arrests at Atlanta’s Emory University and University of Southern California cancelled a graduation ceremony as campus protests against the war in Gaza continue.

Emory officials said protesters not connected with the college entered the campus grounds early on Thursday.

Police used chemical sprays to disperse them when they refused to leave.

A week after protests began at New York’s Columbia University, they have spread to dozens of colleges in the US.

The Emory protesters said they were supporting Palestinians but also voicing their objection to a police training centre in Atlanta.

Plans for the centre have been controversial locally and the project has been dubbed “Cop City” by opponents.

In a statement, Emory said that outside protesters were later joined by “members of the Emory community” and that the group was “disrupting the university as our students finish classes and prepare for finals”.

Several dozen were arrested, the university said, but declined to give exact numbers or say if any had been charged with crimes.

Atlanta Police said that they used chemical irritants but denied reports that they fired rubber bullets against protesters.

One of the protesters shown on video being detained by police identified herself as Noelle McAfee, chair of Emory’s philosophy department.

Ms McAfee said was observing what she described as a peaceful protest when police began to move in and the protesters started to march.

“It went from a peaceful protest to mayhem in the matter of a minute,” she said. She said she froze and was detained.

Also on Thursday, the University of Southern California cancelled its main commencement ceremony scheduled for 10 May, citing new safety measures.

“As a result, we will not be able to host the main stage ceremony that traditionally brings 65,000 students, families, and friends to our campus,” the university said in a statement.

The USC decision comes after police made multiple arrests when confronting protesters there on Wednesday and ordering the dismantling of an encampment.

It is also after USC said earlier this month that Muslim student Asna Tabassum would no longer be permitted to deliver a speech as valedictorian due to unspecified security threats.

The spate of campus protests began at Columbia University in New York City last week. The university called in New York police and more than 100 people were arrested.

The movement against the Israeli war in Gaza has now reached dozens of college campuses across the country.

Activists have been calling for universities to “divest from genocide” and to stop investing large school endowments in companies involved in weapons manufacturing and other industries supporting Israel’s war in Gaza.

Chisato Mimura, a law student and protest leader at Yale University in Connecticut, told the BBC that activists are upset at President Joe Biden as well as their school officials for “quite literally funding and equipping the weapons used in genocide”.

“But instead, what they’re doing is completely putting their full weight behind it,” she added. “We are well aware of the prominent role they are playing.”

Israel strongly denies any suggestion that it is committing genocide in the Palestinian enclave, though the International Court of Justice has said the accusation was “plausible”.

Some of the protests have been accused of antisemitism. A number of Jewish students have said they have felt unsafe at Columbia and at other universities, although other Jewish students have joined the demonstrations.

At Columbia, the university administration have set a midnight deadline to reach a deal with student protesters to avoid further disruption.

In a news conference, university spokesperson Ben Chang said that if no agreement was reached, “we will have to consider options for restoring calm to campus”, but did not outline any specific measures that would be taken.

Mr Chang said the university was preparing for further protests on Thursday evening.

Earlier on Thursday, Minnesota Democratic congresswoman Ilhan Omar visited the campus. Her daughter, Isra Hirsi, was one of the protesters cleared from the university by police last week.

“This is a movement that started with only 70 students,” Ms Omar told the BBC. “And because Columbia University decided to crack down on them and violate their First Amendment [rights], this has now spread nationally and internationally.”

In other recent developments:

The war began when Hamas-led gunmen carried out an unprecedented attack on southern Israel on 7 October, killing about 1,200 people – mostly civilians – and taking 253 others back to Gaza as hostages.

More than 34,180 people – most of them children and women – have been killed in Gaza since then, the territory’s Hamas-run health ministry says.