Top brass is due to touch down on Manus Island on Thursday after fatal violence at an Australian-operated detention centre.

Lieutenant-General Angus Campbell will be backed by additional security staff as conflicting reports continue to circulate about what sparked Monday’s riot, which left an Iranian man dead, almost 80 others injured, and saw Papua New Guinean police fire shots.

“He is authorised to take actions up there that he thinks are appropriate,” Immigration Minister Scott Morrison told the Macquarie Radio, adding that the commander of Operation Sovereign Borders is experienced in such security issues.

PNG police are investigating the riots and Australia has offered assistance.