New York’s Mayor Eric Adams has blamed “outside agitators” for fuelling protests on American campuses as violent clashes erupted on opposite sides of the country.

There were wild scenes at campuses in New York and Los Angeles overnight (AEST) as activism descended into chaos, leading to the arrests of nearly 300 people.

In Los Angeles, Israel-Palestine antagonism played out as Israel supporters wearing masks and wielding sticks attacked a pro-Palestinian protest camp at the University of California.

Footage online shows masked counter-demonstrators – supporting Israel – throwing objects and trying to smash or pull down the wooden and steel barriers erected to shield the encampment.

Some screamed pro-Jewish comments as pro-Palestinian protesters tried to fight them off.

Demonstrators on both sides sprayed each other and fights broke out.

Police said they had responded to a request from UCLA to restore order and maintain public safety “due to multiple acts of violence” within the encampment.

Israeli protesters at the pro-Palestine encampment at the University of California. Photo: Getty

New York police arrested pro-Palestinian demonstrators holed up in a building at Columbia University and removed a protest encampment on Tuesday night.

Adams blamed the protests on outside agitators, but without offering concrete evidence. He did not specify how many, if any, were believed to be external agitators.

“There were individuals on the campus who should not have been there. They were people who are professionals and we saw evidence of training,” Adams said.

“I know that there are those who attempting to say, ‘Well, the majority of people may have been students’. You don’t have to be the majority to influence and co-op an operation. That is what this about.

“This is a global problem that young people are being influenced by those who are professionals at radicalising our children and I’m not going to allow that to happen as the mayor of the city of New York.”

Pro-Palestine demonstrators barricade themselves inside a building at Columbia University. Photo: Getty

Student rallies have spread to dozens of campuses across the US in the biggest outpouring of American student activism since the anti-racism protests of 2020.

The protest camps relate to the October 7 attack on southern Israel by Hamas militants from the Gaza Strip and the ensuing Israeli offensive on the Palestinian enclave.

On Tuesday night (local time), New York police arrested dozens of pro-Palestinian demonstrators holed up in a building at Columbia University and removed a protest encampment that the Ivy League college had sought to dismantle for nearly two weeks.

About 1200 people in southern Israel were killed in the October 7 attack but the Israeli retaliatory assault has killed nearly 35,000 Palestinians, according to Gaza health ministry figures, obliterated much of the enclave’s infrastructure, and created a humanitarian crisis verging on famine.

-with AAP