The protest march that started from Technical Junction was scheduled to end at the Presidential Secretariat after handing over a memorandum.
The protest resulted in a massive traffic jam.
"Three of our colleagues including a female undergraduate have been arrested," President of the Students’ Council of the Kelaniya University, Nandana Sudesh told.
Protesters said rubber bullets had also been fired.
He said one student, injured in the police attack, had been admitted to the National Hospital.
Sudesh said they had conducted the protest march demanding immediate release of eight students who were in the remand prison over an alleged ragging incident, withdrawal of suspension of some students, ending sexual harassment within the university premises and solving students’ welfare problems.
Police said they had been compelled to use tear gas and water cannon as the students were violating a court order preventing protest marches and demonstrations.
Sudesh said police had come to them with a court order, but they had refused to accept it.
Three undergraduates had been remanded till today (16) by the Colombo Fort Magistrate, SSP Jayakody said.