But the Department of Immigration denies that the assault ever occurred.
Refugee Action Coalition's Ian Rintoul says about 20 Serco officers were involved in the incident, although it seems only five or six were directly involved in the assault early today.
Mr Rintoul says the 29 year-old Tamil refugee has been in detention for two and half years, and has injuries to his head, face, neck, his hand and legs.
But the Department of Immigration says there was no assault and the man was taken to the hospital for a medical condition, although it won't comment further.
