The UN human rights chief said on Tuesday he was "troubled" by heavy-handed actions taken by US security forces during attempts to break up pro-Palestinian protests on college campuses.
"I am concerned that some of law enforcement actions across a series of universities appear disproportionate in their impacts," Volker Turk said in a statement sent to journalists, in which he made reference to arrests and sanctions of students.
"It must be clear that legitimate exercises of the freedom of expression cannot be conflated with incitement to violence and hatred," he added.