A Sudanese refugee detainee has received a top human rights award for revealing what he has described as Australia's "inhumane" treatment of asylum seekers.

The 26-year old Abdul Aziz Muhamat was held at the Manus Island detention centre after fleeing violence in Darfur.

Over six years, he sent thousands of WhatsApp messages to a journalist who told his story in a podcast.

The Martin Ennals Award recognised his "extraordinary tenacity and courage".

Mr Muhamat described the camp's conditions, which have long been criticised by the United Nations.

He said he was stripped of his name and referred to as a number- QNK002.

Prisoners were fed through a chain-link fence and treated worse than animals, he added.

Designed to deter refugees from reaching Australia by sea, Manus Island sits off Papua New Guinea.

Another island in the Pacific, Nauru, is also used as an offshore detention centre and the Australian prime minister has just announced he will reopen Christmas Island.