Police in Papua New Guinea have shot a group of protesting university students who were trying to march to Parliament in the capital Port Moresby.
The students say police fired shots directly into the crowd, causing several to be injured.
A major aid agency, which declined to be named as its report is preliminary, said it had information from the university clinic that at least 15 students were wounded, with four killed.
Student Gerald Peni told the ABC police fired shots directly into the crowd when students would not let them arrest the president of the student council.
Port Moresby General Hospital said 10 students had been admitted. "They are in a difficult situation," the admissions officer told Reuters.
Foreign Minister Julie Bishop told reporters in Brisbane that the situation was "a tragedy" and that the government was still trying to determine how many casualties there were.
"We are still seeking to determine the actual outcome" she said. "We call on all sides for calm to de-escalate the tensions."
Ms Bishop said there were about 70 AFP officers there.
"I know students have been shot but we are still trying to determine whether there have been deaths and how many have been injured. We will be monitoring the situation closely."
Thousands of students at the University of Papua New Guinea in the capital of Port Moresby have been protesting and boycotting classes for weeks amid growing political unrest in the Pacific island nation.
The governor of Oro Province Gary Juffa, a critic of the O'Neill government, said on Twitter that he had spoken directly with students at the protest.
"Informed that several were shot," Juffa said, adding that the incident started with an argument between a metropolitan police superintendent and a student.
PNG's opposition made a fourth unsuccessful attempt this week to unseat O'Neill's government via a no confidence bid, gaining some support from members of the leader's own party.