Contact with several tribes on the Andaman islands, set deep in the Indian Ocean, is illegal in a bid to protect their indigenous way of life and shield them from diseases

Members of one of the world's last tribes untouched by modern civilisation have killed an American who ventured illegally onto their remote island, Indian police said Wednesday.

John Allen Chau, 27, was hit by a hail of arrows as he set foot on North Sentinel Island, part of the Indian Andaman Islands, last Saturday, official sources told AFP.

"He was attacked by arrows but he continued walking. The fishermen saw the tribals tying a rope around his neck and dragging his body," the source said.

"They were scared and fled but returned next morning to find his body on the seashore."

North Sentinel is home to the Sentinelese people, believed to number only around 150. To protect their way of life, foreigners and Indians are banned from going within three miles (five kilometres).

Chau had offered local fishermen money to take him to the island, the source said. They took him some of the way and he paddled the rest in a canoe.

Andaman and Nicobar Islands, India

Some Indian media suggested that Chau was a missionary seeking to convert the islanders to Christianity but a local policeman told the News Minute website this was inaccurate.

"He was on a misplaced adventure in (a) prohibited area to meet uncontacted persons," Dependra Pathak told the website.

Media reports also said the fishermen told a preacher in the main town of the Andamans, Port Blair, about the incident and the preacher contacted Chau's family in the United States.

A spokesperson for the US consulate in the southern Indian city of Chennai told AFP only that they were aware of "reports concerning a US citizen in the Andaman and Nicobar Islands".

- Hostile hunters -

The Andamans are also home to the 400-strong Jarawa tribe who activists say are threatened by contact from outsiders. Tourists have previously bribed local officials in a bid to spend time with them.

But the Sentinelese still shun all contact with the outside world and have a record of hostility to anyone who tries to get close.

In 2006, two Indian fishermen who moored their boat to sleep were killed when the vessel broke loose and drifted onto North Sentinel, according to Survival International, a group protecting tribal people's rights.

The Sentinelese hunt and gather in the forest, and fish in the coastal waters.

The island was hit by the devastating 2004 tsunami that swept across the Indian Ocean but not much is known about the impact it had on the reclusive inhabitants.

After the tsunami one member of the tribe was photographed attempting to fire an arrow at an Indian Coast Guard helicopter.

Indian authorities make periodic checks on the tribe from boats anchored at a safe distance from shore.

Survival International, based in London, said that the "tragedy" of the American's death "should never have been allowed to happen".

"The Indian authorities should have been enforcing the protection of the Sentinelese and their island for the safety of both the tribe and outsiders," it said.

"Instead, a few months ago the authorities lifted one of the restrictions that had been protecting the Sentinelese tribe's island from foreign tourists, which sent exactly the wrong message, and may have contributed to this terrible event."

- Arrests -

Since the Indian authorities keep away from the island, it was unclear whether Chau's killing will have legal repercussions.

Indian police said a murder case had been registered against "unknown" tribespeople and that six fishermen and one other person were arrested.

"The investigation in this matter is on," senior police officer Deepak Yadav said in a press release.

Police official Pathak said the authorities were consulting "anthropologists and tribal welfare experts" to work out how best to retrieve the victim's body.