Controversial Australian Senator Pauline Hanson has backed the Sentinelese tribe's "immigration policy" after the group reportedly killed an American missionary looking to convert the group.

John Chau, a devout Christian, was believed to be shot to death with arrows after travelling to the North Sentinel Island to covert its local tribe to Christianity.

International advocacy groups have called for the tribe to be left alone, and they have found an unlikely ally in Ms Hanson.

The Senator has gone as far as to ask the Australian Senate if they will support the Sentinelese people's "zero-gross immigration policy".

On Tuesday she asked the Senate acknowledge that the tribe are likely the "last pre-Neolithic tribe in the world and possess a unique culture a way of life that should be cherished and protected".

"Even small levels of migration would have a devastating and irreversible effect on the beautiful and unique culture and way of life of the Sentinelese people," the motion says.