Nine people were arrested at the University of Minnesota on Tuesday when campus police broke up a pro-Palestinian encampment shortly after it was set up -- prompting hundreds of students to walk out of their classes in protest as encampments continued sweeping across U.S. colleges.

Tents and signs were erected on the Northrop Mall of the Twin Cities campus around 4 a.m. and the cops showed up about two hours later, the Star Tribune reported.

"The group was asked to disperse by 7 a.m. and told they would be arrested if they chose to stay past that time," the university said in a statement. "Some of those present chose to disperse and continue peacefully protesting, but nine chose to remain and were arrested without incident."

Student organizer Merline Van Alstine told Minnesota Public Radio that the arrested activists "were sitting in the middle of the encampment with their arms crossed together and chanting for Gaza, and then one by one they pulled them off."

Campus police removed the tents and Hennepin County jail records showed nine people were booked on misdemeanor trespassing charges, according to the Star Tribune.

On Tuesday afternoon, about 300 people staged a walkout at the school, with junior Mirabai Dornfest telling MPR she left her Sociology of Gender class to oppose the police action and show support for those who were arrested.

Dornfest, who is Jewish, said the move was "in line with my morals as a person, as a student, as someone who feels in solidarity with oppressed peoples, as a person whose family is a bunch of immigrants."

Last week, more than 100 protesters were arrested when the New York City police broke up encampment at Columbia University but the protest there has continued and the encampment is bigger than ever, overhead images show.

On Monday, 133 people were arrested outside an encampment at New York University in New York City and 60 people, including 47 students, were arrested after refusing to leave an encampment at Yale University in New Haven, Connecticut, according to the Associated Press.

Three protesters were also arrested at California State Polytechnic University, Humboldt, after demonstrators occupied a building Monday night, AP said.