A leading expert on isolated Amazon tribes in Brazil has been killed by an arrow which hit him as he approached an indigenous group, according to friends and a police witness.

Rieli Franciscato, who was 56 years old, was an official for the Brazilian government’s indigenous affairs agency Funai, where he had worked to set up reservations to protect tribes in the country.

Mr Franciscato was hit by an arrow above the heart on Wednesday in the forest near the Uru Eu Wau Wau reservation in the western state of Rondonia as he moved towards a previously uncontacted indigenous group.

“He cried out, pulled the arrow from his chest, ran 50 metres and collapsed, lifeless,” a policeman who accompanied the expedition said.

The Kaninde Ethno-Environmental Defence Association, which Mr Franciscato helped set up in the 1980s, said the group had no ability to distinguish between a friend or a foe from the outside world.

Gabriel Uchida, a photojournalist in the region, told AFP news agency that the tribe was “a peaceful group” when they were last seen in June.

“This time, there were only five armed men, a war group. That means something must have happened for them to seek ‘revenge’,” Mr Uchida said.