Some 200 indigenous activists and fishermen have been occupying the main construction site at Brazil's controversial Belo Monte dam in the Amazon and are demanding government involvement in the negotiations.

"We want to be heard. We want a close representative of President Dilma Rousseff to come and see us," chief Valdemir Munduruku, one of the leaders of the occupation, told AFP by telephone Monday.

Five indigenous tribes are calling for legislation under which they would have to be consulted prior to any official decision affecting them with respect to the dam's construction.

"They should consult us but instead they are sending the police and soldiers. They are denying access to our lawyer," the chief said.

A press spokeswoman for the Norte Energia consortium in charge of the dam's construction in northern Para state confirmed the occupation Monday.

"Work has stopped on the main site, where most of the turbines will be set up," she said from Brasilia, adding that the protesters' demands had been forwarded to federal authorities.

Six thousand workers have been idle for the past five days and Friday some 80 police arrived to protect the site.

"Today we are going to leave the site to give a press conference and release a letter with our demands," chief Munduruku said.

"You are pointing your weapons at our heads. Your soldiers and war trucks are besieging our lands. You are eliminating our fish," said an excerpt from the letter.

"What we want is simple. You must implement the law on prior consultation of indigenous people," the letter concluded.

Protesters have accused Norte Energia of backtracking on accords signed in June after 150 indigenous people occupied the Pimental area for three weeks.

They complain that fishing in the area is no longer possible and there is no drinking water.

Belo Monte, which is being built at a cost of $13 billion, is expected to flood an area of 500 square kilometers (200 square miles) along the Xingu River, displacing 16,000 people, according to the government.

Some NGOs have estimated that some 40,000 people would be displaced by the massive project.

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

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

The federal government plans to invest a total of $1.2 billion to assist the displaced by the time the dam is completed in 2019.

The first turbine is set to begin operating in 2015 and the last one in 2019.

The native peoples want their lands demarcated and non-indigenous people removed from them. They also are demanding better health care and access to drinking water.