SYDNEY (AP) — A refugee being held in an Australian immigration camp on the Pacific island nation of Papua New Guinea was found dead in an apparent suicide on Monday, sparking outrage from fellow refugees and advocates who say officials failed to treat him despite a long history of mental illness.

Hamed Shamshiripou, a 28-year-old refugee from Iran, was found hanging from the branch of a tree near an elementary school by students on Monday morning, Papua New Guinea police said in a statement. The school is in the Manus Island town of Lorengau, where Shamshiripou had been staying at a transit center for refugees awaiting resettlement.

An autopsy was being conducted, but Police Commissioner Gari Baki said there were no suspicious circumstances surrounding the man's death. Shamshiripou had previously attempted to commit suicide, Baki said.

Australia refuses to resettle any asylum seekers who try to reach its shores by boat. Instead, the country pays Papua New Guinea and the Pacific island nation of Nauru to house them in camps condemned as draconian by human rights advocates.

Behrouz Boochani, an asylum seeker and journalist from Iran who has been detained on Manus since 2013, said in a telephone interview that Shamshiripou had a long history of mental illness. Shamshiripou had been sent to live in the island's so-called transit center, which is supposed to provide temporary accommodations for refugees waiting to be resettled elsewhere. Many refugees don't want to go there because they view it as unsafe.

Shamshiripou's behavior was erratic, and he was often found wandering the streets of Lorengau dressed only in his underwear, Boochani said. Several months ago, Boochani says he and around 100 refugees signed a letter asking immigration officials to treat Shamshiripou. They got no response, Boochani said. Four days ago, Boochani says, Shamshiripou tried to kill himself with a razor.

"Hundreds of refugees are sick — they are damaged physically and mentally in this prison and Australia doesn't care," Boochani said. "Australia is responsible because Australia took him by force to this island. Australia made him crazy. Australia has kept him in this prison for more than three years. Australia ... took him by force to the transit center and Australia left him without any protection there and now he died. So Australia is responsible."

Manus Provincial Police Commander Chief Inspector David Yapu said in an email that Shamshiripou tried to kill himself last year while in police custody, but was stopped by officers on duty.

The fate of the more than 2,000 asylum seekers living in Papua New Guinea and Nauru has become a political nightmare for Australia's government, which insists its policy of refusing to resettle any asylum seekers who try to reach Australia by boat is necessary to dissuade them from attempting the dangerous and often deadly ocean crossings. The policy, however, has resulted in scores of refugees languishing for years on the islands. There have been several high-profile suicides and attempted suicides at the camps, including a man who killed himself by setting himself on fire in Nauru last year.

Australian officials thought they had found a solution after hammering out a deal with the Obama administration, which pledged to resettle the refugees in the U.S. But President Donald Trump was enraged upon learning of the agreement, and so far none of the refugees have been moved to the U.S.

Daniel Webb, director of legal advocacy at Australia's Human Rights Law Centre, said refugees and asylum seekers being held at the camps are in danger, and must be immediately resettled in Australia.

"Like every one of the 2,000 innocent people being warehoused by our government on Nauru and Manus, this man deserved decency and respect. This man deserved a chance to build a life in freedom and in safety," Webb told reporters. "But instead, our government chose cruelty. Instead, our government chose to detain him for four years on a remote island. So this man lost his freedom and then he lost his hope and now he's lost his life. It is an absolute tragedy."