The murder trial in Papua New Guinea for two men accused of beating an asylum seeker to death on Manus Island is due to start next week.

Reza Barati, a 23-year-old Iranian, died during a riot at the Australian-run detention centre on February 17 last year.

In July, police arrested security guard Louie Efi and soon afterwards arrested Salvation Army worker Joshua Kaluvia.

The Papua New Guinean men were both charged with murder.

The case has been listed in the Manus Island court for Monday.

Refugee advocates said asylum seekers have been asked to give evidence over the next three weeks.

Some asylum seekers are reportedly nervous about their safety while testifying, others have already confirmed they will take the stand.

Last year, PNG police said they were looking for three more suspects, one Papua New Guinean and two expatriates, in relation to Mr Barati's death.

More than 1,000 asylum seekers are being detained on Manus Island as part of the Federal Government's offshore processing policy.

The violence at the detention centre in Papua New Guinea was "eminently foreseeable", according to a Senate committee report into the incident.

About 70 asylum seekers were injured, some seriously, in what the Government described as a "disturbance" on Manus Island.