Behrouz Boochani, 36, was sent to Manus Island in Papua New Guinea after fleeing Iran in 2013
Behrouz Boochani, 36, was sent to Manus Island in Papua New Guinea after fleeing Iran in 2013 Amnesty International / JASON GARMAN

An Iranian asylum seeker and award-winning author held in an offshore Australian detention camp for more than six years said Thursday he had arrived in New Zealand, and was celebrating "freedom".

Behrouz Boochani was sent to Manus Island in Papua New Guinea after fleeing Iran in 2013. He was picked up on a vessel packed with asylum seekers attempting to reach Australia from Indonesia.

The 36-year-old journalist later won the Victorian Prize for Literature for a book detailing his life under Australia's harsh offshore detention policy.

"I just arrived in New Zealand. So exciting to get freedom after more than six years," Boochani tweeted on Thursday.

"Thank you to all the friends who made this happen."

Under a policy meant to deter asylum-seekers from reaching Australia by boat, Canberra has for years sent arrivals to remote Pacific camps on Nauru and Papua New Guinea's Manus Island for processing, barring them from ever resettling in Australia.

The UN, rights groups and leading health professionals have slammed Canberra for its treatment of detainees, as stories of violent riots, self harm, dire living conditions and even murder have emerged from the camps over the years.