Refugee advocate Ian Rintoul says Nauru is still mourning the death of Fariborz Karami, a 26-year-old Kurdish asylum seeker from Iran, who was found dead on Friday morning in his family's tent.
A commemoration of Mr Karami's life was held on Sunday night at the family camp on Nauru where he and his family were held, Mr Rintoul said.
He said on Sunday the "threat level" for certain areas in the camp was at three out of a maximum of five and tension was high as services to refugees including the provision of medication had been reduced.
"Everyone is wondering who is next. With so many nationalities being denied entry to the US, many people are left thinking that there is only one way off Nauru now."
Mr Rintoul said the death was tragic and unnecessary.
The company managing the centre raised the threat level after a scuffle when people in the camp followed the dead man's family to the camp's main complex, Mr Rintoul said.
"They have raised that threat level, they are very aware of just how well liked and the impact that it's had across the island, and there's a lot of despair, a lot of concern for a very well liked young man."
Mr Rintoul said the Immigration Minister and Australia's offshore detention policy were responsible for the death.
The Nauru government said it was waiting for a doctor to come from Australia to do a post mortem examination to confirm the cause of death.