The New York Police Department made at least 100 arrests overnight, with most at Columbia University. Arrests were also made at City College of New York, officials said.

Many of those taken into custody are still being processed at police headquarters.

-ABC News’ Aaron Katersky

Clashes between opposing groups of protesters at the University of California Los Angeles included "multiple acts of violence," prompting university officials to ask police to enter the campus, the Los Angeles Police Department said.

Officers responded to assist campus police "to restore order and maintain public safety," the LAPD said.

State and local politicians said they were monitoring the situation, with Los Angeles Mayor Karen Bass calling the violence "absolutely abhorrent and inexcusable."

Gov. Gavin Newsom said his office had been in contact with law enforcement leadership.

-ABC News' Bonnie Mclean, Amanda Morris and Kevin Shalvey

At least 25 people were arrested at CUNY's City College of New York campus as police confronted protesters early Wednesday, the university said in a statement.

University officials said they asked the New York Police Department for assistance in clearing protesters, including a "large crowd" of people who had marched from Columbia University to City College.

The school described a "series of violent indents" that it said put public safety at risk over the last six days.

"This includes a fire Sunday night at the Marshak Science Building caused by use of a flare gun that brought FDNY to campus, clashes with public safety, an attempted break-in at Shepard Hall tonight, and a break-in at the Administration Building tonight that included the vandalizing of offices and smashing glass doors," the university said in a press release early Wednesday.

Police entered the campus just before midnight and began making arrests, the university said.

"Students have a right to demonstrate peacefully and exercise their First Amendment rights," the university said. "Tonight's actions were taken in response to specific and repeated acts of violence and vandalism, not in response to peaceful protest"

-ABC News' Jessica Gorman and Kevin Shalvey

After Columbia University was cleared of encamped protesters Tuesday night, the school said it its Morningside campus was immediately restricted to students who live there and workers providing essential services.

"Effective immediately, access to the Morningside campus has been limited to students residing in residential buildings on campus (Carman, Furnald, John Jay, Hartley, Wallach, East Campus and Wien) and employees who provide essential services to campus buildings, labs and residential student life (for example, Dining, Public Safety, and building maintenance staff). There is no additional access to the Morningside campus," the notification read.

The university said the restrictions would stay in place "until circumstances allow otherwise."

-ABC News' Victoria Arancio

University of California President Michael V. Drake addressed the ongoing protests at UCLA that "turned violent" overnight, announcing in a statement on Wednesday an "independent external review" has been ordered.

The university summoned mutual aid from LAPD officers to "restore control" to the protest, according to Drake, who noted, there were 15 injuries, including one hospitalization, that stemmed from the protest.

"My office has requested a detailed accounting from the campus about what transpired in the early morning hours today," Drake said.

"But some confusion remains, therefore we are also ordering an independent external review of both UCLA’s planning and actions, and the effectiveness of the mutual aid response," Drake said.

UCLA's own chancellor, Gene D. Block, also promised an investigation.

"We are still gathering information about the attack on the encampment last night, and I can assure you that we will conduct a thorough investigation that may lead to arrests, expulsions and dismissals," Block told the campus community in a note Wednesday afternoon.

Block, in his note, said it was "a group of instigators" who came to Royce Quad to "forcefully attack the encampment that has been established there to advocate for Palestinian rights."

He called the overnight violence "utterly unacceptable."

"However one feels about the encampment, this attack on our students, faculty and community members was utterly unacceptable. It has shaken our campus to its core and — adding to other abhorrent incidents that we have witnessed and that have circulated on social media over the past several days — further damaged our community’s sense of security," his letter read.