Police in Sao Paulo fired tear gas Monday to disperse protesters supporting a subway strike that has unleashed transport chaos three days before the Brazilian mega-city hosts the World Cup kick-off.
A group of about 150 protesters set fire to piles of garbage to block a central avenue in the Brazilian business hub, prompting some two dozen riot police to fire stun grenades and then tear gas to disperse them.
The demonstrators were backing a five-day-old strike by subway workers that has posed a major headache for the sprawling city of 20 million people ahead of Thursday's opening match between Brazil and Croatia.
Demonstrators from various activist groups shouted "No to repression!" before police broke them up.
But as three police helicopters hovered overhead, the protest regrouped and grew to about 300 people who marched up the same street chanting "There won't be a Cup, there will be a strike!"
Police also used a stun grenade against a separate group of about 70 picketing strikers, said union president Altino Melo dos Prazeres.
Police said they had detained 13 of the workers for damaging a door and interfering with colleagues' work at the station, where officers used tear gas and truncheons to disperse strikers last Thursday.
The union has reduced an initial demand for a 16.5-per cent wage hike to 12.2 per cent, but the government is offering only 8.7 per cent.
A labour court ruled Sunday that the strike was illegal and imposed a $222,000 fine for every day it continues, but the union voted to press on with the walkout.
But Prazeres said he was confident the strikers had the upper hand.
"I don't believe the government wants to thwart this Cup," he told AFP.