Survival got involved after Brother Joao Carlos Martinez from Spain, Father Cesar Avellaneda from Colombia and Father Ronildo Franca from Brazil, missionaries on the Raposa Serra do Sol indigenous reserve, were released on 12 January following three days in captivity.
All three had been campaigning for the removal of 7,000 settlers - rice cultivators, farmers and cattle ranchers - working in collusion with local politicians. They were taken hostage when a mob of 200 non-Indian settlers invaded their mission and ransacked a hospital and school catering for the Indian population.
Fiona Watson, Survival campaigns coordinator, said: "The Catholic Church is perceived by the local politicians and rice cultivators as being very active when it comes to the rights of indigenous peoples and they want to stop this.
-Indigenous groups are seen as obstacles to progress - the only areas left with forest cover are those belonging to them."
And although Brazilian environment minister Marina Silva is pro-indigenous, she is fighting against a rising tide of big business; US food giant Cargill is currently involved in clear-cutting forest for the rapidly growing expansion of the GM soya crop.
Survival is also disappointed with Brazilian president Luiz Inacio "Lula" da Silva. "At the beginning of his presidency a year ago he talked of indigenous land rights but in terms of delivery nothing has been done," said Watson.
The pan-indigenous people's organisation COAIB, who Lula is due to meet early this year, burnt Lula's manifesto last November.
A spokesman for the Indigenous Council of Roraima said: "Ratification of Raposa Serra do Sol is the barometer measuring the attitude of the Lula government. If it acts now, Indians throughout Brazil will take this as a sign of the government's commitment to upholding their rights."
In December Brazil's minister of justice announced that Lula would ratify the area as a reserve. Although the 3.95 million acres territory has been mapped and demarcated, it still needs that presidential signature promised since 1998.
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