LOS ANGELES (AP) — Police arrested pro-Palestinian protesters on college campuses across the country overnight, notably at the University of California, Los Angeles, where chaotic scenes played out early Thursday as officers in riot gear surged against a crowd of demonstrators.

Police removed barricades and began dismantling demonstrators' fortified encampment at UCLA after hundreds of protesters defied orders to leave, some forming human chains as police fired flash-bangs to break up the crowds.

The California Highway Patrol said at least 132 protesters were arrested. Some sat with their hands behind their backs on the sidewalk, their hands bound with zip ties. Others were loaded onto Los Angeles County Sheriff's buses and taken to a downtown inmate processing center, spokeswoman Julia Tafoya said. She did not know how many were arrested.

The action came after officers spent hours threatening arrests over loudspeakers if people did not disperse. A crowd of more than 1,000 had gathered on campus, including inside a barricaded tent encampment. Protesters and police shoved and scuffled as officers encountered resistance. Video showed police pulling off protesters' helmets and goggles as they were detained.

With police helicopters hovering, the sound of flash-bangs — which produce a bright light and a loud noise to disorient and stun — pierced the air. Protesters chanted at the officers, "Where were you last night?" Late Tuesday, counterprotesters attack the encampment and the UCLA administration and campus police took hours to respond.

Tent encampments of protesters calling on universities to stop doing business with Israel or companies they say support the war in Gaza have spread across campuses nationwide in a student movement unlike any other this century. The ensuing police crackdowns echoed actions decades ago against a much larger protest movement protesting the Vietnam War.

Demonstrations — and arrests — have occurred in almost every corner of the nation. Seventeen people were arrested on criminal trespass charges Wednesday at the University of Texas at Dallas after demonstrators refused to comply with law enforcement orders to remove an encampment from the school's main walkway, a university spokeswoman said in a statement Thursday.

Yale University police arrested four people, including two students, Wednesday night after around 200 demonstrators marched to the school president's home and the campus police department, school officials said. Protesters ignored repeated warnings that they cannot occupy parts of campus without permission, school officials said in a statement Thursday.

The protest group Occupy Yale said campus police were violent during the arrests and did not issue warnings. The group posted a video on Instagram showing officers taking one person to the ground and pinning another to a sidewalk.

"A peaceful protest," Occupy Yale said. "Police officers seized, pushed, and brutalized people. Is this what you call keeping campus safe?"

In Oregon, police began to clear pro-Palestinian rights demonstrators out of the Millar Library at Portland State University, which they have been occupying since Monday.

They spray-painted graffiti inside and knocked over or piled up furniture to create barricades. Portland State said on social media Thursday that campus would remain closed because of the police activity.

University President Ann Cudd said Wednesday that about 50 protesters vacated the library after administrators promised not to seek criminal charges, expulsion or other discipline if they left peacefully, but others — including non-students — remained. Portland police said Thursday that 15 police vehicles were set on fire overnight; it was not immediately clear if that was related to the protest.

University of Minnesota officials meanwhile reached agreement with protesters to end an encampment on the Minneapolis campus. Interim President Jeff Ettinger said in an email Thursday to the campus community that nearby buildings would reopen at noon and that protesters agreed not to disrupt final exams or commencement ceremonies. That followed similar agreements at Northwestern University in suburban Chicago and Brown University in Rhode Island.

The protests at UCLA appeared to be getting the most attention. Iranian state television carried live images of the police action, as did Qatar's pan-Arab Al Jazeera satellite network. Live images of Los Angeles also played across Israeli television networks.

President Joe Biden on Thursday defended the students' right to peaceful protest but decried the destruction and disorder of recent days.

Israel has branded the protests antisemitic, while Israel's critics say it uses those allegations to silence opposition. Although some protesters have been caught on camera making antisemitic remarks or violent threats, protest organizers — some of whom are Jewish — call it a peaceful movement to defend Palestinian rights and protest the war.

California Highway Patrol officers poured into the UCLA campus by the hundreds early Thursday. Wearing face shields and protective vests, they held their batons out to separate them from demonstrators, who wore helmets and gas masks and chanted: "You want peace. We want justice."

Police methodically ripped apart the encampment's barricade of plywood, pallets, metal fences and dumpsters, then pulled down dozens of canopies and tents. The number of protesters diminished through the morning, some leaving voluntarily with their hands up and others detained by police.

The law enforcement presence and continued warnings contrasted with the scene Tuesday night, when counterdemonstrators attacked the pro-Palestinian encampment, throwing traffic cones, releasing pepper spray and tearing down barriers. Fighting between the two sides continued for hours before police stepped in. No one was arrested, but at least 15 protesters were injured. Authorities' tepid response drew criticism from political leaders, Muslim students and advocacy groups.

By Wednesday afternoon, a small city sprang up inside the reenforced encampment, with hundreds of people and tents on the quad. Demonstrators rebuilt the makeshift barriers around their tents while state and campus police watched.

Some protesters said Muslim prayers as the sun set, while others chanted "we're not leaving" or passed out goggles and surgical masks. They wore helmets and headscarves, and discussed the best ways to handle pepper spray or tear gas as someone sang over a megaphone.

Outside the encampment, a crowd of students, alumni and neighbors gathered on campus steps, joining in pro-Palestinian chants. A group of students holding signs and wearing T-shirts in support of Israel and Jewish people demonstrated nearby.

The crowd grew as the night wore on as more and more officers poured onto campus.

Ray Wiliani, who lives nearby, said he came to UCLA on Wednesday evening to support the pro-Palestinian demonstrators.

"We need to take a stand for it," he said. "Enough is enough."

California Gov. Gavin Newsom denounced the delayed law enforcement response on Tuesday and UCLA Chancellor Gene Block promised an investigation. The head of the University of California system, Michael Drake, ordered an "independent review of the university's planning, its actions and the response by law enforcement."

"The community needs to feel the police are protecting them, not enabling others to harm them," Rebecca Husaini, chief of staff for the Muslim Public Affairs Council, said during a news conference Wednesday.

Meanwhile, police cleared protest encampments at schools across the U.S., resulting in arrests, or were closed up voluntarily. In New York, those included the City College of New York, Fordham University, Stony Brook University and the University of Buffalo. Others nationwide included the University of New Hampshire in Durham, Northern Arizona University in Flagstaff, and Tulane University in New Orleans.

On Tuesday night, police burst into a building occupied by war protesters at Columbia University, breaking up a demonstration that had paralyzed the school.

Columbia's chapter of the American Association of University Professors condemned the school's leadership on Thursday for asking New York police to remove the protesters. The chapter said "the horrific police attack on our students" is now "shamefully on view for the whole world to see."

At the University of Wisconsin in Madison, a scrum broke out early Wednesday after police with shields removed all but one tent and shoved protesters. Four officers were injured. Four people were charged with battering law enforcement.

The nationwide campus demonstrations began at Columbia on April 17 to protest Israel's offensive in Gaza, which followed Hamas launching a deadly attack on southern Israel on Oct. 7. Militants killed about 1,200 people, most of them civilians, and took roughly 250 hostages. Vowing to stamp out Hamas, Israel has killed more than 34,000 Palestinians in the Gaza Strip, according to the Health Ministry there.

U.S. college campuses have become a flashpoint, with school leaders facing intense scrutiny over their handling of allegations of antisemitism and the right to free speech. The presidents of Harvard and the University of Pennsylvania resigned following questions at a congressional hearing about whether calls on campus for the genocide of Jews would violate the school's conduct policy.