A policeman peers behind his riot shield inside Ana Rosa subway station during the fifth day of metro worker's protest in Sao Paulo. Picture: Kai Pfaffenbach

Sao Paulo -

Police in Sao Paulo fired tear gas on 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 street 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 up the protest. Several helicopters could later be seen hovering overhead.

Police also used a stun grenade against a separate group of about 70 striking workers who had gone into a central metro station to try to convince supervisors to join the strike, said union president Altino Melo dos Prazeres.

Police are holding about a dozen of the workers at the station, where officers used tear gas and truncheons to disperse strikers last Thursday, a union official said.

The union has reduced an initial demand for a 16.5-percent wage hike to 12.2 percent, but the government is offering only 8.7 percent.

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.

Rising inflation and a sluggish economy have tarnished the World Cup glow in Brazil, fuelling the anger of strikers and protesters who say the $11-billion budget would have been better spent on education, health and transport.

The protests come as World Cup teams continue arriving in Brazil, with reigning champions Spain touching down Sunday night.

The United States, France, Argentina, Uruguay, Ecuador, Costa Rica, Honduras and Cameroon are all expected Monday.

After that all but five of the tournament's 32 teams will be on the ground.

But the chaos gripping Sao Paulo Ä the latest in a wave of strikes and protests around the tournament Ä has distracted the usually passionate footballing nation from the World Cup buildup.

The five-line subway system has been partially operating, but trains were not arriving at Corinthians Arena, which will host the opening game.

Authorities are keen to resolve the latest labor dispute and avoid further embarrassment in a World Cup hit by delays and cost overruns even before it has started.

Corinthians Arena has become a symbol of the problems besetting the tournament.

At the weekend workers were racing to finish the 61 600-capacity stadium, which has been chronically behind schedule and over-budget.

Work on the 12 host stadiums has also been overshadowed by accidents that have killed eight workers. Three of the deaths were at Corinthians.

President Dilma Rousseff, who is seeking reelection in October, insists the money spent on the tournament will leave a legacy of modernised airports and transport infrastructure that will benefit Brazil for years.

But many of the promised projects have been shelved, adding to protesters' anger.

A year ago during the Confederations Cup, a World Cup dress rehearsal, more than a million people flooded the streets, some trashing property and clashing with police.

Recent protests have been smaller, but activists are vowing to revive last year's “Tropical Spring” during the World Cup. - Sapa-AFP