US President George W Bush arrived in Brazil on Thursday amid protests at his visit that turned violent at the start of his five-nation Latin America tour.
In Sao Paulo, Brazil's largest city and financial capital, a massive demonstration poured down the main avenue. Protesters carried signs reading "Bush out of Iraq" and "Down with the Number One Terrorist George Bush".
Organisers said the demonstration drew at least 30,000 people; police put the number at 10,000.
The peaceful demonstration turned violent after a group of protesters entered a prohibited area along the avenue.
Protesters hurled rocks and sticks at police, who fired tear gas and rubber bullets. The clash left 16 police officers and some six protesters injured.
<b1>Meanwhile, marchers marking International Women's Day chanted anti-Bush slogans.
"The women are demonstrating to say 'no' to North American imperialism, 'no' to neo-liberalism and 'no' to the domination of one people over another," Maria Fernanda Marcelino, member of the march organising committee, said.
Hours before the US president landed in Sao Paulo, some 200 members of a far-leftist group hurled rocks at the US consulate.
On Wednesday, thousands of Brazilian farmers had occupied offices to protest against agro business and Bush.
In Colombia, on the second day of anti-Bush demonstrations, hooded protesters threw rocks and firecrackers at riot police using water cannon in a pitched four-hour battle. No injuries were reported.
"Murderer of Iraqis not welcome in Colombia" said one sign. "Get out, evil emperor Bush," said another, ahead of the US leader's arrival on Sunday.
Bush, who has been accused by critics of neglecting Latin America, pledged this week to back social justice and prosperity in the region and unveiled new aid schemes for education, housing and health.
But he faces a region that has recently elected or re-elected leftists who oppose his views, including in Bolivia, Ecuador, Nicaragua and Venezuela, where Chavez has called Bush everything from a "tyrant" to the "devil."
Chavez, the closest ally of Cuba's communist leader Fidel Castro, arrived in Argentina late Thursday for a two-day trip that will also take him to Bolivia.
Although the firebrand Venezuelan has said the timing was a coincidence, he will take part in an anti-Bush protest in Buenos Aires.
When Bush visits Uruguay on Friday, Chavez will headline an "anti-imperialist rally" in a 40,000-seat Buenos Aires football stadium.
Anti-Bush demonstrations were also planned in Uruguay.
Bush and his policies, particularly the Iraq war and the fight against drug trafficking, are widely unpopular in Latin America.
In Brazil, trade unionists and leftist movements, including the Workers Party (PT) of President Luiz Inacio Lula da Silva, planned more protests during Bush's stay. The White House downplayed the protests.
"The president enjoys traveling to thriving democracies where freedom of speech and expression is the law of the land," said Gordon Johndroe, a White House spokesman.
"He brings a positive agenda that will demonstrate the benefits of democracy in such areas as economy, health, education, housing for Brazilians as well as all the citizens of the hemisphere," Johndroe said.
In addition to Brazil, Uruguay and Colombia, Bush will visit Guatemala and Mexico during his trip, which ends on Wednesday.
In Sao Paulo, he was scheduled to meet Lula on Friday to discuss trade and a partnership on the production and use of ethanol, an alternative fuel. The two countries are the world's biggest ethanol producers.