Brazilian mining company Samarco has agreed to a $366 million damage bill after its tailings dam burst, spreading toxic waste over hundreds of kilometres, killing 10 people, and flattening entire villages.

Samarco, a joint venture of Australian mining giant BHP Billiton and Brazilian firm Vale, has signed a “preliminary commitment” guaranteeing “payment for preventive emergency mitigation, repair or compensation measures”, Brazilian prosecutors said in a statement.

But the final amount they pay could be several times higher. 

Disaster struck Brazil's south-eastern state of Minas Gerais on November 5, when the dam ruptured and sent a flood of mining waste and muddy water from Samarco's iron ore mine down into the local environment.

The massive flow knocked out power and water supplies in the area, destroying the village of Bento Rodrigues.

Investigators have now found that up to 500 kilometres of the River Doce is contaminated.

“We know that the amount of damages could be much greater, but the agreement establishes a firm legal guarantee,” prosecutor Carlos Eduardo Ferreira Pinto said.

The damage bill comes after the Brazilian court froze close to $110 million from Samarco's accounts to cover potential damages to victims.

Under the terms of the newly-signed deal, the company must pay the first $183 million within 10 days, and come up with the other half in a month’s time.

The government has appointed an independent auditor to monitor Samarco's distribution of the funds, to ensure it “exclusively” targets costs related to the deadly spill.

Brazilian president Dilma Rousseff has also announced fines of $94 million, which will be paid separately to the damages.

Experts say it should be just the start, with Deutsche Bank analysts expecting the overall clean-up cost to top $1.4 billion.

While BHP – the world’s largest mining company – has managed to avoid much of the fallout from the widespread deaths and contamination, Vale’s offices in Brazil have been hit with a barrage of vocal protests.

Over a hundred people have held a demonstration outside Vale's headquarters in Rio, chanting “Vale, you killed me!”

“We are demonstrating in solidarity with the victims and against the damage from this ecological crime committed by Vale,” organiser Marcelo Castanheda said.

“We don't even know the full extent of it yet.

“We, members of civil society, want to pressure the participants in this tragedy so that they pay.”

Mud-smeared protesters held placards reading “It was not an accident!”

“I am putting a curse on Vale, it will be bankrupted,” Wuako, a member of the Assurini Indigenous tribe, told reporters.