The US Interior Department has decided to hand the bones of Kennewick Man - one of the oldest skeletons to be found in North America - to five native-American tribes who have claimed him as an ancestor.

The decision is seen as a setback for scientists who say the 9,000-year-old bones could hold the key to the identity of the first inhabitants of the Americas.

The skeleton was found in 1996 in the Columbia River, near the tribes' aboriginal lands in southern Washington state.

US Interior Secretary Bruce Babbitt said the remains were "culturally affiliated" with the five tribes, who want them buried immediately.

Mr Babbitt, quoted by the Associated Press news agency, said he was "persuaded by the geographic data and oral histories of the five tribes that collectively assert they are the descendants of people who have been in the region of the Upper Columbia Plateau for a very long time".

Doubts about origins

Kennewick Man - named after the place where the skeleton was found - has forced anthropologists to rethink theories about where the original Americans came from.

Radiocarbon dating of the remains has put their age at between 9,320 and 9,510 years old.

Experts say Kennewick Man appears to be linked to the people of Polynesia and southern Asia.

The find has fuelled speculation that the earliest humans in North America came not via a land bridge between Russia and Alaska - a long-held theory - but by boat or some other route.

So far tests have failed to identify the racial origin of the skeleton - samples were sent to three laboratories, but none managed to extract DNA for analysis.

But eight anthropologists have filed a lawsuit at a federal court for the right to study the bones. The remains are being kept at the Burke Museum of Natural and Cultural History in Seattle.