Asylum seekers, already angry about the uncertainty they faced, were repeatedly told they would remain in Manus Island's overcrowded detention centre indefinitely at an incendiary pre-riot meeting, footage obtained exclusively by Fairfax Media shows.

The meeting brought to a head tensions that had simmered for months over the failure to process their claims for refugee status, and it was a catalyst for the violence that began less than two hours later, culminating in the killing of detainee Reza Barati.

Nearly two hours of video chart the meeting's descent into combative chaos as detainees vented their frustrations on PNG and Australian officials, who in turn delivered scripted answers that underscored the hopelessness of the detainees' situation.

No fewer than five times, PNG immigration official Jeffrey Kiangali told the detainees that assessing their asylum claims would be a ''very lengthy process'' with ''no definite timeframe''.

He also repeatedly stressed they were ''free to go home'' any time, but if they chose to stay, they would be stuck in the detention camp ''for as long as it takes to process your claims''.

His answers to questions put by the detainees at a meeting 12 days earlier were jointly written by Australian and PNG officials.

Mr Kiangali also told the detainees that any misbehaviour might affect their refugee claims - a suggestion refugee lawyers said was inappropriate.

Mr Kiangali said: ''Your behaviour and conduct at this centre will also be taken into consideration during your refugee status determination process.''

In protests that followed, some of the detainees taunted PNG nationals outside the centre, but in the meeting one Iranian stressed that their grievance was not with PNG people.

''We just talk about your government, not your people,'' the man declared. ''Your people are really lovely and we love them but, the thing is, your government shouldn't accept this.''

Others expressed concerns about their safety if their claims were accepted and they were permanently resettled in PNG.

''I don't feel protected in PNG,'' another told the meeting. ''PNG is a high-crime country … Can you protect me? Can you protect all these people?''

According to the departmental inquiry headed by Robert Cornall, the meeting brought the tensions to a flashpoint, with detainees believing they would be on Manus Island for up to four years.

The meeting also underscores that many asylum seekers were simply upset they had been transferred to PNG when they wanted to come to Australia.

''I seek refuge in Australia. Why was I taken by force to this country?'' one detainee demanded of Mr Kiangali.

Daniel Webb of the Human Rights Law Centre said it was inappropriate for immigration officials to tell asylum seekers the success of their refugee claims was conditional on their good behaviour.

He said: ''Refugees have rights. The governments of Australia and PNG must respect them instead of threatening to ignore them unless people are completely and utterly compliant whilst being detained indefinitely in inhumane conditions.''

It is understood a video has been submitted to a Senate inquiry by security firm G4S. The firm declined to comment when contacted by Fairfax Media.

But on ABC's 7.30 on Tuesday night, the company's managing director of immigration services said they were ''saddened by the events of that night''.

Chris Manning insisted that G4S did not know which of its staff might have been involved in the fatal bashing Reza Barati, saying there were allegations, but it had not identified perpetrators, just passed all information to PNG police.

Mr Manning said it was not for G4S to sift the evidence, its role was to support the police inquiry ''to ensure that anybody who has broken the law in this brutal and horrific way is brought to justice''.

with AAP

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