Brazilian riot police have used tear gas against protesters in Sao Paulo, three days before the World Cup opening game in the city's main stadium, Radio New Zealand reports.
A group of about 150 strikers and protesters set fire to piles of rubbish to block a central avenue in the city's business hub, prompting officers to fire stun grenades and then tear gas.
The demonstrators are supporting a strike by subway workers, the latest in a wave of protests and strikes that has swept Brazil before of the World Cup and elections in October.
Sao Paulo metro workers have been on strike since Thursday, creating traffic chaos in one of the world's most congested cities.
The state subway company has offered an 8.8 per cent pay rise but this has been rejected by the strikers.
If the strike runs on until Thursday, it could affect the opening match between hosts Brazil and Croatia.
Brazilian President Dilma Rousseff has said she would not allow violent demonstrations to mar the World Cup preparations for which have been beset by construction delays and strikes.
But President Rousseff has said her government would “fully guarantee people's security” during the tournament.
Thousands of extra police and soldiers will be deployed to ensure the matches get under way smoothly.