Australia’s treatment of asylum seekers sent to offshore processing centers is cruel, inhuman and degrading and it violates international law, the United Nations’ human rights office said Friday.

It called for an investigation and punishment of those responsible for an outbreak of violence at a center in Papua New Guinea that houses asylum seekers sent there after trying to get to Australia.

Clashes between inmates and guards at the Manus Island processing center in Papua New Guinea this week left one person dead and 77 injured. Ravina Shamdasani, a spokeswoman for the United Nations human rights office in Geneva, noted reports that private security guards employed at the Manus Island center were involved in the violence and added that “states maintain their human rights obligations when they privatize delivery of services such as security, and must take steps to investigate, redress and punish human rights abuses by third parties.” Prime Minister Tony Abbott elected in 2013 partly on the promise of a tough policy toward migrants and asylum seekers, said the government would not succumb to “moral blackmail” and would ensure that the camps were run “fairly, if necessary, firmly.”