The Brazilian official in charge of indigenous affairs resigned Friday amid protests by natives locked in land feuds with white farmers and opposing construction of a huge dam in the Amazon.

Marta Azevedo, president of the National Indian Foundation, or FUNAI, decided to step down, saying she needed to undergo medical treatment and could not carry out her duties, a government statement said.

Azevedo, who had taken up her post in April 2012, quit as President Dilma Rousseff faces the most violent protests by the country's natives since she came to power two and a half years ago.

The violence has been sparked by a spate of disputes in central Mato Grosso do Sul. An indigenous Terena Indian died last week during a police operation ordered to expel 1,000 natives who occupied a white-owned farm in the state.

One percent of the Brazilian population controls 46 percent of the cultivated land.

Armed with bows, arrows and spears and wearing face paint, feathers and straw clothing, 200 indigenous people massed Thursday in central Brasilia, where they aired their complaints outside Rousseff's office.

"We demand an end to the violence against indigenous people, we want the return of our ancestral lands occupied by landowners," said Gilma Veron, an ethnic Terena from the hamlet of Buriti in Mato Grosso do Sul.

The federal government has deployed a 110-strong contingent of the National Force, a special police unit, in the Mato Grosso do Sul town of Sidrolandia, where indigenous Terena are occupying the white-owned farm to demand the return of their ancestral lands.

Rousseff has said her government will respect any decision made by judicial authorities on the land dispute, but she favors negotiations "to prevent conflicts, deaths and injuries."

Indigenous Mundukuru opposed to construction of the huge Belo Monte dam in the Amazon also traveled to Brasilia this week to air their own grievances, insisting that they were not consulted before the work began as required by law.

The $13 billion project is expected to flood a 500-square-kilometer (200-square-mile) area along the Xingu River, displacing 16,000 people, according to the government.

The dam, expected to produce 11,000 megawatts of electricity, would be the third-biggest in the world, after China's Three Gorges and Brazil's Itaipu dam in the south.

Indigenous groups say the dam will harm their way of life. Environmentalists have warned of deforestation, greenhouse gas emissions and irreparable damage to the ecosystem.

And Brazil's powerful landowners scheduled their own protest in Mato Grosso do Sul next week against invasions of their ranches by area natives, the Agriculture and Livestock Confederation of Brazil said.

Indigenous peoples represent less than one percent of Brazil's 194 million people and occupy 12 percent of the national territory, mainly in the Amazon.