Five of the detainees say they're eyewitnesses to the alleged murder of the Iranian asylum seeker who died in the February riots.
Their lawyers say the detainees have received death threats and believe the Australian and Papua New Guinea governments cannot guarantee their safety.
Barrister Jay Williams took affidavits from them after getting access to the detention centre in March before he was ordered out of PNG.
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Sydney law firm Stacks Goudkamp has briefed Mr Williams to act for the detainees.
Senior associate Ruth Hudson says her firm has made two applications, including lodging a writ that accuses the Australian and Papua New Guinean governments of crimes against humanity.
She said that in addition to the orders being sought from the High Court, there's an urgent need for an inquiry or Royal Commission into what's occurred at the detention centre.
Solicitor Ruth Hudson tells Greg Dyett there's an urgent need for an inquiry into Manus Island.
A spokesman for the Minister for Immigration Scott Morrison has issued a statement to SBS saying it would be inappropriate to comment on any matters before the courts.
The minister's office says the transferees at the Manus Island processing centres are lawfully in PNG and that transferees wishing to return to a country where they have a right of residency can have such travel facilitated.

