The University of California, Los Angeles, canceled all classes on Wednesday after a night of violent clashes between pro-Palestinian protesters and counterprotesters, one of the most striking conflicts yet at an American university over the war in Gaza.
Administrators said in an email on Wednesday that police officers would remain stationed throughout campus. They urged students and faculty members to avoid the quad that was occupied by a pro-Palestinian encampment, where the detritus from a night of chaos — trash, broken pieces of wood, trampled clothing — speckled the ground.
As the campus awoke early Wednesday, students and other curious onlookers leaned against the barricades at the encampment, silently taking videos or snapping photos. A police helicopter continued to hover overhead, and a large Palestinian flag at the center of the camp swayed in the wind.
The protests turned violent hours after administrators declared the encampment illegal and threatened to suspend or expel any student protesters. A group of about 200 counterprotesters stormed the camp, and the two sides fought, at times throwing punches and objects.
Officers from the California Highway Patrol arrived on campus about 1:15 a.m., according to Officer Michael Nasir. At about 3:30 a.m., officers wedged themselves between the groups, and the violence began to de-escalate. There were no arrests, said Officer Sergio Garcia of the C.H.P., though the university did not immediately respond to requests about whether the campus police had taken anyone into custody.
Aidan Woodruff, 19, a first-year cello performance major, had just learned that classes were canceled when he arrived on campus Wednesday morning to practice his instrument. Woodruff said he knew at least 50 students who had spent the past two days studying for midterms, only to learn that all exams for the day had been postponed.
“The general response from the student body is just frustration,” he said. “Blocking access to classes, not being able to get to where they need to go. There are definitely students who feel strongly about the causes, but a big part of it is people coming in from the general L.A. area and putting on a demonstration here that’s causing so much disruption.”
The university said that the two main buildings beside the encampment, Royce Hall and Powell Library, would remain closed through at least Friday.
The U.C.L.A. Palestinian Solidarity Encampment, which says it is made up of students, faculty members and community members, condemned the school’s “pretense of student safety” in a statement, saying that campus police, external security and law enforcement failed to protect them from counterprotesters as “we screamed for their help.”
The Jewish Federation Los Angeles said it was “appalled” at the violence that occurred on campus, and that the counterprotesters did not represent the Jewish community or its values. The federation criticized the U.C.L.A. chancellor, Gene Block, and the school’s administration for creating an environment that has made students feel unsafe and called on him to meet with leaders of the Jewish community to discuss safety measures.
Hussam Ayloush, the director of the Greater Los Angeles Area office of the Council on American-Islamic Relations, urged Rob Bonta, the state’s attorney general, to investigate what he characterized as a lack of response by the campus police and the Los Angeles Police Department.
“U.C.L.A. and other schools must ensure that students can continue to peacefully protest the genocide in Gaza without facing attacks by violent pro-Israel mobs,” Mr. Ayloush said in a statement.
Jonathan Wolfe, Emily Baumgaertner and Claire Fahy contributed reporting.