By Gary Duffy
BBC News, Sao Paulo
Brazil's disappearing rainforests have long been of concern
Efforts to combat illegal logging in the Amazon will be intensified after an attack by 3,000 people on government offices, Brazilian officials have said.
Environment Minister Carlos Minc said the government would not be intimidated by the violence in which vehicles were burned and a hotel was attacked.
The protests began after officials confiscated illegally felled wood.
Federal troops have been asked to bolster security in the town of Paragominas in the northern Para state.
The authorities say that at the height of the violence, directed against environmental inspectors working in Paragominas, more than 3,000 people were involved.
The government environment agency, Ibama, said the protests began after officials seized more than 400 cubic metres (14,000 cubic feet) of wood which had been illegally cut down on a nearby Indian reservation.
Some of the highest levels of deforestation in the Amazon have happened in the area around Paragominas, and the town has been part of a major effort by government officials to combat illegal logging.
During the violence on Sunday, protesters stole 14 trucks with confiscated logs, and tried to invade a hotel where government agents were staying.
Vehicles belonging to the agents and an office containing computers and paperwork were also set on fire and destroyed.
Mr Minc said the government would not back down in its efforts to combat illegal deforestation.
On the contrary, he said, the government would intensify its actions, and would punish those responsible for the violence.
Earlier this year rioting broke out in the town of Tailandia, which is also in the state of Para, as the government began "Arc of Fire" - a major operation designed to combat illegal logging in the Amazon.
The latest violence is further evidence that efforts to protect the Amazon run contrary to the interests of some powerful economic forces - Ibama says wood company bosses and truck drivers were involved in the protests.