"The failure of federal authorities to guarantee the right of indigenous people to their land, through demarcation and ratification of many indigenous territories ... has contributed to attacks on Indians," Amnesty said.

There were an estimated 6 million Indians in Brazil when the Portuguese arrived. The Indian population currently stands at over 700,000, having risen from 400,000 in the late 1980s due to better medical care.

But Amnesty said that if the government does not make Indian rights a priority "violence and chronic poverty will continue to threaten their very existence."

Many local communities across Brazil have clashed with Indians over what they claim are their ancestral lands. In a particularly violent clash, at least 26 diamond miners were killed in a clash with Indians last year.

Most of the time, however, it is the Indians who are the victims. At least 14 Indian children have died of malnutrition on an Indian reserve in the state of Mato Grosso do Sul this year, Indian rights groups said this month.

In addition, Amnesty cited the 2003 beating death of a 72-year-old Kaiowa Indian leader in front of his family. The suspects, who are expected to go on trail later this year, were removing him from ancestral lands.

"The Brazilian authorities have repeatedly failed to intervene to prevent loss of life. Even when there have been repeated warnings that serious violence is likely to occur in the context of indigenous land disputes or invasions, as in the case of the Xukuru in the state of Pernambuco or the Cinta Larga in Rondonia, no action has been take," Amnesty said.