Jewish students at the London School of Economics and members of the university’s Palestinian Society clashed during an Israel Apartheid Week protest.

The Palestinian Society protesters created a mock checkpoint Monday outside a campus building, stopping students by asking for identification and reportedly harassing Jewish students.

Counter-protesters, said to be members of the Students’ Union Jewish Society, threw water balloons at the Palestinian Society protesters, spurring a fight that injured at least one student, the Jewish Chronicle reported. University security had to separate the protesters.

“The Union of Jewish Students has consistently opposed these fake security checkpoints as being intimidating against Jewish students,”  a union spokesman told the Jewish Chronicle. “These stunts reduce what is a serious and complex situation between Israelis and Palestinians into theatrical provocations that can only ever prove divisive here on British campuses.”

The school’s Students’ Union said in a statement that it supports the right to peaceful protest but condemned the violence. The union said it would undertake an investigation of the incident in conjunction with the school.