Amnesty International on Friday called for an independent investigation into the killing of a Guarani Indian chief in Brazil's western state of Mato Grosso do Sul.

It urged that letters be sent to the Brazilian justice ministry to request a through and independent probe into the killing of 59-year-old Nisio Gomes and the kidnapping of three young Indians .

Last Friday, 42 heavily armed, hooded men burst into the Kaiowa Guarani community in the village of Amambai, near the border with Paraguay, killing Gomes and abducting a child and two youths.

"The federal authorities must ensure the safety of the Kaiowa Guarani community and urgently address their land claims," said Guadalupe Marengo, Amnesty Internationals deputy Americas program director.

"Unfortunately, this is not an isolated incident. For years, gunmen in the midwest of Brazil have launched violent attacks with impunity against indigenous communities who attempt to occupy their ancestral lands," she added.

The human rights group said that two days before last week's attack, gunmen had reportedly threatened to take Gomes' life.

She noted that landowners and ranchers in Mato Grosso do Sul frequently use hired gunmen and private security companies to intimidate indigenous communities fighting for their constitutional rights to their ancestral lands.

Thursday, federal officials in Brasilia said they were close to reaching a deal with Mato Grosso do Sul authorities to secure a demarcated territory for the Guarani Indians.

But the Indigenous Missionary Council with skepticism, saying the agreement dates back to 2008 but has never been implemented.

"We doubt that the government has sufficient political will to do it, because Mato Grosso do Sul is a state dominated by agroindustrial interests," said Saulo Feitosa, deputy secretary of CIMI, an agency defending indigenous rights.