Manus riots inevitable: former guard

Bribing guards for food, living with the constant threat of violence and queuing for hours in the tropical sun for basic necessities.

That's the image of everyday life for detainees at the Manus Island detention centre painted by a former security guard, who described the atmosphere before February's fatal riots as a "powder keg" waiting to explode.

Riots over two nights at the Papua New Guinea facility led to dozens of injuries and the bashing murder of Iranian asylum seeker Reza Barati, whose head was crushed with a rock.

Steven Kilburn, a former G4S employee turned whistleblower, said staff at the centre repeatedly warned that living conditions needed to be improved or tensions would spill over into violence.

"We were constantly told it was just too hard," Mr Kilburn told a Senate inquiry into Mr Barati's death on Wednesday.

Mr Kilburn, at times visibly emotional, said detainees would sometimes spend entire days queuing up in the sun for meals and lived in shanty-like conditions with no privacy or cleanliness.

Staff also saw detainees stockpiling cigarettes so they could bribe PNG officials in the mess halls.

"They were constantly having to bribe people to get a bit more food, to get some condiments or to get a piece of fruit," Mr Kilburn said.

The inquiry was told drunk PNG soldiers would harass detainees and threaten female staff, while police on duty chewed the mild narcotic betel nut despite rules forbidding its use.

PNG locals resented detainees for receiving better food and medical treatment, with religious differences also adding to tensions between the groups.

Mr Kilburn said despite witnessing serious incidents - including a Somali teenager bashed so badly he couldn't speak or eat - he wasn't invited to give evidence to the independent review into Mr Barati's death.

G4S sent him and other officers an email after the incident reminding them of their confidentiality agreements, a factor Mr Kilburn attributed to many staff not coming forward.