Police in Papua New Guinea have clashed with students on the University of PNG campus in the capital, Port Moresby.
Security officers say students burnt two university buses during a protest last night.
Police say they fired warning shots to disperse the students.
University teachers outside the campus said they had heard of police officers assaulting students, and had seen an ambulance enter the university grounds.
Students have been holding a boycott of classes over the past fortnight to protest against the university's new grading system.
On the 11th of July protesters burnt cars used by the vice-chancellor and the bursar.