Protesters demonstrating in Brazil in support of teachers receiving better pay in the Brazilian cities of Rio de Janeiro and Sao Paulo have clashed with police. Downtown Rio was packed with more than 10,000 people marching peacefully. But as it got dark, some protesters threw firebombs at public buildings and riot police responded with tear gas.
A similar protest in São Paulo also ended in violent confrontation with police after many banks were ransacked by hooded protesters.
Brazil's security situation is a challenge to cities that will play host to the 2014 World Cup and 2016 Olympic Games.
The latest demonstration took place over several hours and was peaceful at first. But once night fell, violent incidents broke out as at least 20 "black bloc" anarchists smashed a City Hall gate while others broke into banks and tried to break into ATMs. Some bank branches were set alight.
Demonstrators also torched a bus on busy Rio Branco Avenue, and took furniture out of banks to use in barricades as the stand-off off with police continued.
Teachers have been agitating for a pay increase for two months. About 50,000 people were estimated to have marched to support them before the violence broke out, but police would only confirm the 10,000 estimate.
Brazilian police poured into a dozen slum areas of Rio de Janeiro over the weekend continuing a drive to pacify the poor neighborhoods despite accusations of police brutality that have called the tactic into question.
Backed by Brazilian marines in armored vehicles, more than 1,000 police poured into a dozen of the slum neighborhoods in northern Rio just after dawn, meeting no resistance.
"It's one more step in the direction of peace," said Rio de Janeiro governor Sergio Cabral. After sweeping through the area, police began going house to house to conduct searches and question suspects.
"That population has been clamoring for this for a long time," Rio Police Chief Jose Mariano Beltrame said.
The deployment of so-called Police Pacification Units aims to wrest control of poor hillside neighborhoods from drug gangs and bring down violent crime in the city that will play host to the 2014 World Cup and 2016 Olympic Games.
But the police tactics have come under scrutiny after 10 members of one pacification unit were arrested this week for the torture and killing of a bricklayer who disappeared in July from Rocinha, the city's largest favela with 70,000 inhabitants.
Amarildo de Souza's disappearance set off protests by outraged residents demanding authorities explain what happened to him. His body has not been found, but investigators say he was tortured to death by members of a pacification unit who were seen on a surveillance tape taking him into custody.
Police inspector Ellen Souto, who is heading the police probe into the death, said 22 other people have alleged they also were tortured with electric shocks and hot wax.
Cabral, under attack over the police scandal, defended the pacification units, UPP.
"I lament the conduct of those police officers, which was abominable, but without a doubt it will not be a mark against the UPP," he said. He added investigations of crimes like De Souza's disappearance was only possible when communities were pacified.
"How many crimes went unpunished before the police's arrival in the hillsides," he asked.