Forest fires raging in Brazil’s northern Amazon jungle have spread to the reserve of the Yanomami indians, one of the world’s last hunter-gatherer tribes.

Environment minister Marina Silva urged farmers not to light any more fires during the dry season and promised compensation to those who do not burn to prepare land for sowing.

Authorities estimate about 23 square miles of forest have been destroyed.

The Yanomami are one of the only true surviving Neolithic tribes and had lived in isolation until the late 1970s when they were identified on aerial surveys.