Indigenous activists occupied the headquarters of a federal agency here Tuesday as part of mounting protests against government policies and the construction of a controversial dam in the Amazon.

The natives arrived in the Brazilian capital a week ago for talks with authorities after occupying one of the Belo Monte dam's building sites.

Unhappy with the outcome, about 150 activists invaded the headquarters of the National Indian Foundation (Funai), the federal agency handling indigenous affairs, late Monday.

"We want respect for the constitution in which the indigenous rights are clearly spelled out," chief Valdenir Munduruku told AFP.

"The government is putting forward various decrees, which flout our rights over our lands with the creation of dams," he added. "We want prior consultation over all these dams."

Armed with bows, arrows and spears, and donning face paint, feathers and straw garb, the indigenous Munduruku, Arara, Kaiapo and Xipaia -- including women and children -- came from the northern state of Para.

"Respect our rights," proclaimed a huge banner on the agency's gate.

Belo Monte, a $13 billion project aiming to produce 11,000 megawatts of electricity, is expected to flood a 500-square-kilometer (200-square-mile) area along the Xingu River, displacing 16,000 people, according to the government.

It would be the third-biggest dam in the world, after China's Three Gorges and Brazil's Itaipu in the south.

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

Amid bitter land feuds with white ranchers, the protesters are also railing against bills that would affect recognition of native lands and authorize mining on them.

The long-simmering protests boiled over in April when leaders of 121 ethnic groups from around Brazil stormed the House of Deputies to demand their rights and accused President Dilma Rousseff of siding with the powerful agribusiness sector responsible for the country's vital farm exports.

"The mobilization of the indigenous community is a reaction to the assault on their rights. The government has been slowing the process of recognizing their rights and indigenous rights enshrined in the Constitution are being jeopardized by initiatives in a Congress controled by the agribusiness lobby," said Cleber Buzatto, executive secretary of the Indigenous Missionary Council.

Also taking part in the Brasilia protests are ethnic Terena from the central state of Mato Grosso do Sul where one of their members died during a recent police operation ordered to expel 1,000 natives who occupied a white-owned farm.

Last year, ethnic Guarani-Kaiow� from central Brazil also made the headlines when they resisted eviction from a white-owned ranch they said was located on their ancestral lands.

Meanwhile the influential National Confederation of Agriculture (CNA) scheduled a farmers' protest for Friday.

"They are not respecting the rights of rural producers," said CNA President Katia Abreu.

Indigenous peoples represent less than one percent of Brazil's 194 million people.