Police lift a pro-Palestinian demonstrator from the ground on the University of Virginia campus, in Virginia. AP

Police on Saturday arrested at least 25 pro-Palestinian protesters and cleared an encampment at the University of Virginia, the university said in a statement, as US campuses braced for more turmoil during graduation celebrations.

Tensions flared at UVA's campus in Charlottesville, where protests had been largely peaceful until Saturday morning, when police officers in riot gear were seen in a video moving on an encampment on the campus' lawn, cuffing some demonstrators with zip-ties and using what appeared to be chemical spray.

Students across the US have rallied or set up tents at dozens of universities to protest the months-long war in Gaza and call on President Joe Biden, who has supported Israel, to do more to stop the bloodshed in Gaza. They also demand their schools divest from companies that support Israel's government, such as arms suppliers.

The University of Virginia said in a news release that protesters had violated several university policies including setting up tents on Friday night and using amplified sound.

Jim Ryan, UVA's president, wrote in a message that officials had learned that "individuals unaffiliated with the university" who presented "some safety concerns" had joined protesters on campus.

It wasn't immediately clear how many of those arrested were UVA students.

Police and pro-Palestinian demonstrators stand across from one another in Charlottesville, Virginia. AP

A group called UVA Encampment for Gaza that said earlier this week it had set up the encampment condemned the university's decision to call in police in a post on Instagram.

Dozens of people were arrested for criminal trespass outside the Art Institute of Chicago at a demonstration on Saturday after the institute called in police to remove protesters it said were illegally occupying its property, the Chicago Police Department said on X.

Elsewhere, confrontations did not escalate into arrests. In Ann Arbor, pro-Palestinian protesters briefly disrupted a commencement ceremony at the University of Michigan.

Videos shared on social media showed dozens of students wearing the traditional keffiyeh headdress and graduation caps and waving Palestinian flags as they walked down the center aisle of Michigan Stadium among cheers and boos from a crowd of thousands.

Police with riot shields form a line across from pro-Palestinian demonstrators in Virginia. AP

The ceremony continued and campus police escorted the protesters toward the back of the stadium, but no arrests were made, according to Colleen Mastony, a spokesperson for the university.

"Peaceful protests like this have taken place at U-M commencement ceremonies for decades," Mastony said in a statement. "The university supports free speech and expression, and university leaders are pleased that today’s commencement was such a proud and triumphant moment."

Contrasting views over Israel's war in Gaza have erupted, sometimes violently, across US campuses over the last couple of weeks.

Many of the schools, including Columbia University in New York City, have called in police to quell the protests.

Police have so far arrested over 2,000 protesters at colleges around the country.

Police with riot shields detain a pro-Palestinian demonstrator on the University of Virginia campus, in Virginia. AP

The University of Michigan is one of the many universities which altered their security protocols for graduation ceremonies.

The anti-war protests have been staged in response to Israel's offensive in Gaza, which it launched after a Hamas attack on Oct. 7 that Israel says killed 1,200 people. Israel has killed over 34,000 people in retaliation, according to Gaza health authorities, and flattened the Palestinian territory.

Reuters