Survival International, a group that advocates for the rights of tribal people, has called for the cancelation of a search for the body of a US missionary who was killed while attempting to preach to people on North Sentinel Island.

Key points: Survival International director Stephen Corry says any attempt to recover Mr Chau's body is "extremely dangerous"

Survival International director Stephen Corry says any attempt to recover Mr Chau's body is "extremely dangerous" The risk of a deadly epidemic of flu, measles or other outside disease is "very real", Mr Corry says

The risk of a deadly epidemic of flu, measles or other outside disease is "very real", Mr Corry says The group calls for Mr Chau's body to be left alone and for restrictions around the island to be beefed up again

Indian authorities have been struggling to recover the body of John Allen Chau, who was reportedly shot with a bow and arrow and buried on a beach on the island.

Survival International director Stephen Corry said the organisation was advocating for Indian authorities to abandon their efforts to recover Mr Chau's body.

"Any such attempt is extremely dangerous, both for the Indian officials, but also for the Sentinelese, who face being wiped out if any outside diseases are introduced," he said.

"The risk of a deadly epidemic of flu, measles or other outside disease is very real, and increases with every such contact.

"Such efforts in similar cases in the past have ended with the Sentinelese attempting to defend their island by force.

"Mr Chau's body should be left alone, as should the Sentinelese.

"The weakening of the restrictions on visiting the island must be revoked, and the exclusion zone around the island properly enforced."

John Allen Chau was killed when he went ashore on North Sentinel Island. ( Instagram: johnachau )

Sentinelese people are 'a treasure'

Indian officials have travelled repeatedly in recent days near the remote island where Mr Chau was killed by people who have long resisted the outside world.

But they have not set foot onto North Sentinel Island since the killing, and it remains unclear if they will.

Director-general of police on the Andaman and Nicobar island groups, Dependera Pathak, said the Sentinelese people "are a treasure".

"We cannot go and force our way in. We don't want to harm them," he said.

Indian Police have mapped the spot on the island where they believe Mr Chau's body is buried. ( Supplied: Andaman and Nicobar Police )

The Sentinelese, who scholars believe are descendants of Africans who migrated to the area about 50,000 years ago, survive on the small, forested island, which is approximately 60 square kilometres in size, by hunting, fishing and gathering wild plants.

Almost nothing is known of their lives, except that they attack outsiders with spears or bows and arrows.

Mr Chau was killed by islanders in mid-November after paying fishermen to smuggle him to the island, where outsiders are effectively forbidden by Indian law.

The fishermen told authorities that they saw the Sentinelese bury Mr Chau's body on the beach.

The notes Mr Chau left behind say he wanted to bring Christianity to the islanders.

A boat carrying police and other officials approached North Sentinel on Friday and Saturday, watching the Sentinelese through binoculars.

On Saturday the tribesmen were armed with spears and bows and arrows, but they did not attempt to shoot them at the authorities, Mr Pathak said.

"We watched them from a distance and they watched us from a distance," he said.

Officials have not given up on recovering the body, he said.

But they are moving very gingerly, studying the 2006 killing of fishermen whose boat had drifted onto the island.

"We are looking carefully at what happened then, and what [the Sentinelese] did," he said.

"We are consulting anthropologists to see what kind of friendly gesture we can make."

The islanders buried the two fishermen on the beach in 2006, but dug up the corpses after a few days and propped them upright.

Authorities apparently never recovered those bodies, and the killings were never investigated.

North Sentinel Island is approximately 60 square kilometres and the exact population is unknown. ( AP: Gautam Singh )

'The cause of death should be known'

There has been no significant contact with the Sentinelese for generations, and the exact population is not known.

Anthropologists used to occasionally drop off gifts of coconuts and bananas, but even those visits were stopped years ago.

Delhi University anthropologist PC Joshi said he understood why authorities want to recover the body.

"If there is a death, then the cause of death should be known. It's important," Professor Joshi said.

"Of course, we can't prosecute [the islanders]."

He also said it may already be too late to learn much from the body, since the heat and humidity on North Sentinel will cause rapid decomposition.

"Ultimately, it's becoming futile," he said.

The Sentinelese are generally considered the last pre-Neolithic tribe in the world, and are protected by a 1956 law that designates the areas where they live as tribal reserves, with little access for outsiders.

It is illegal to get within 3 nautical miles of the island, and in 2017 the Indian Government also introduced laws that forbid taking photographs or making videos of the Andaman tribes.

But earlier this year, the Government issued a notification exempting foreign nationals from needing special permits to visit more than two-dozen islands, including North Sentinel and others inhabited by indigenous people.

However, Mr Chau did not have one of these permits, police said.

Notes Mr Chau left behind say he wanted to bring Christianity to the islanders. ( Instagram: jonachau )

AP/ABC

