Protesters in Brazil have set fire to buses and trucks for the second consecutive night on the outskirts of the country's largest city, Sao Paulo.
Riot police responded with tear gas and at least six people were arrested, the BBC reports.
Protesters were demanding free public transport. High transport costs triggered protests in Sao Paulo in June that later spread across Brazil.
The clashes came as President Dilma Rousseff announced a plan to improve public transport in the city.
Friday's protests began with a march through the city that lasted about three hours.
Violence erupted when a section of the crowd broke off and attacked a bus terminal in the city centre, police say.
Masked protesters, reportedly including members of the so-called Black Bloc anarchist group, set light to a bus and vandalised cash machines and ticket turnstiles.
At one point a police colonel was struck by a rock and had to be rescued by fellow officers, Brazil's O Globo newspaper reports.
As police moved in, protesters fled, setting up barricades in some parts of the city centre.