By Tom Gibb in Sao Paulo
There have been street confrontations in the Brazilian capital, Brasilia, during a march to protest against corruption and energy rationing.
The police say some 30,000 people took part in the march but that the trouble was started by a small group of punks and anarchists who started to throw bottles and stones at police lines.
In response, the police fired teargas, even into the podium in front of the Congress from which speeches were being made.
They also used a water cannon, and mounted police charged the protesters. At least eight people were reported injured.
What is perhaps remarkable is that there have not been more protests like this, given what many Brazilians think of their politicians and the government.
Some 30,000 people took part in the march
Opinion polls show the popularity of President Fernando Henrique Cardoso has plummeted because of the energy crisis.
The government blames lack of rain in a country which relies completely on hydro-electricity, but most Brazilians blame lack of government planning.
The latest corruption case filling the headlines is not helping the government's cause.
The powerful president of the Senate, Jader Barbalho, is accused of having a part in selling titles for fictitious farms when he was agrarian reform minister, and of being associated with a scheme which defrauded more than $1bn from development projects in the Amazon.