The bodies are said to have been found in indigenous reservations, where only federal police can investigate.

Although mining is banned on Indian reservations, the prospectors say they paid for permission to look there.

The prospectors have clashed before with indigenous people on remote reservations in Rondonia.

However, it is not clear what specifically set off the attacks.

The state is considered one of the main diamond reserves in South America.

Police say they have still not reached the area to confirm the deaths, but have been in contact with other prospectors trying to recover the bodies of their colleagues.

Rondonia Governor Ivo Cassel has been discussing the situation with officials in the capital Brasilia.

"The recent events show that firm and rapid action must be taken," he said. "We can't just watch the conflicts and deaths over diamonds. It's up to the federal government to take firm action to resolve the problem."