Blood, or a symbolic equivalent, was thrown on the Australian High Commission in Wellington decrying the latest death of an asylum seeker on Manus Island.

On Thursday posters were also put up in the Thorndon diplomatic precinct of refugees who have died in the Australian offshore detention centres in Papua New Guinea.

This week, Iranian asylum seeker Hamed Shamshiripour, 31, was the fifth detainee to die on Manus Island.

SUPPLIED On Thursday, the Australian High Commission in Wellington was targeted with a red substance over the latest death in custody of an asylum seeker on Australia's notorious Manus Island detention centre in Papua New Guinea.

Al Jazeera reported he was found hanging from a tree near the East Lorengau refugee transit centre on the island on Monday.

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The media outlet reported refugees on Manus Island were questioning initial reports that he had committed suicide after injuries were reportedly found on his body.

CAMERON BURNELL/STUFF Human rights lawyer Michael Bott said the situation on Manus Island was "profoundly offensive - it's inexcusable.''

A lawyer acting for the family of Iranian refugee Shamshiripour has called for an inquest into his death.

George Newhouse says Shamshiripour's family in Iran awoke to see photos online of their son hanging from a tree on Manus. Refugee activists say foul play can't be ruled out.

"The family don't know what to believe," Newhouse told reporters in Sydney on Wednesday.

HANDOUT Detainees sit inside accommodation at the Manus Island detention centre in Papua New Guinea, February 11, 2017.

The lawyer is calling on the Australian government to investigate Shamshiripour's death.

"Government officials knew about his fragile condition and they left him to die," he said.

Peace Action spokeswoman Emma Cullen said the Wellington group was anonymously provided with images of the Wellington protest and it fully supported the actions.

GETTY IMAGES Papua New Guinea's Manus Island detention centre in October, 2016.

Cullen said the asylum seekers were being treated like prisoners and their human rights were constantly ignored.

These pics were shared with us anonymously & we are sharing bc we believe it is an important action. Kia kaha to all those on Manus & Nauru https://t.co/2gg01bTBPb — Peace Action WGTN (@PeaceActionWGTN) August 10, 2017

"They knew this man had been suffering with his mental health. This death and the others show the Australian government has blood on its hands," Cullen said.

New Zealand should push for its "token offer" to take 150 asylum seekers to be taken up, she said.

In 2013, New Zealand offered to take up to 150 refugees from centres on Nauru and Manus Island, an offer which Australia initially rejected, due in part to fears it could provide a backdoor into Australia via citizenship.

Human rights lawyer Michael Bott said Australian Prime Minister Malcolm Turnbull's stance was at odds with international laws and human rights laws.

"It's profoundly offensive – it's inexcusable. You have people fleeing brutal regimes, deprived and fearful and they've committed no wrong but they're effectively in prison for the crime of trying to stay alive."

Its soft stance on the issue made New Zealand complicit – to a degree – in the abuse, Bott said.

A police spokeswoman said police were investigating the incident at the High Commission but only forensic tests would be able to determine what the blood-like substance was.

"We do not condone protests of this nature and are liaising with local authorities on this matter," a spokesperson for the Australian High Commission in Wellington said.

- Stuff, AAP