World Cup: Tournament begins, Brazil gives away own 1st goal

But the five-time world champions shocked their fans by giving away an own goal 11 minutes into their first game against Croatia at the Corinthians Arena in front of 61,600 fans including 12 heads of state.

Defender Marcelo was almost in tears after he steered the ball into his own net from a Croatian cross. But Brazilian hero striker Neymar equalised in the 29th minute.

Brazilian police put up a ring of steel around the stadium to keep protesters away from the gala debut of the four-week spectacle that Brazil has spent more than 11 billion dollars to prepare for.

But anarchist demonstrators in black shirts and masks lit bonfires of rubbish a few kilometers (miles) from the arena after armoured police sought to quell protests in the hours before the opener.

World Cup preparations have been dogged by months of protests, reflecting widespread public anger over the money spent.

But Sao Paulo and other cities largely went quiet as the game started. Yellow and green flags hung from many buildings. Gutemberg Santos, 42, said his t-shirts and flags had sold like hot cakes. "It has been a good day, everyone is happy," he said.

But protesters who last year brought chaos to the Confederations Cup rehearsal tournament had vowed to march on the Sao Paulo stadium.

But riot police responded forcefully, chasing protesters up a main avenue and firing tear gas in the middle of oncoming traffic, forcing cars decorated with the Brazilian flag to weave their way through the chaos.

A cannister fired by police hit and injured a CNN journalist and an AFP correspondent saw one woman in tears clutching her arm.

In Rio de Janeiro, striking ground staff briefly blocked a road leading to the city's international airport.

Around 1,000 protesters also gathered in the city centre, a small group of them scuffling with police, who arrested four people.

Most of the other World Cup cities were calm. But some took no chances. In Belo Horizonte, shops were closed.

Brazil's President Dilma Rousseff has accused opponents of waging a "systematic campaign" against the World Cup and warned that a repeat of last year's violence would not be tolerated.

The scene inside Corinthians Arena was a world apart from the protests just up the road, as more than 600 dancers in colourful costumes joined pop superstars Jennifer Lopez and Pitbull to put on a lavish opening ceremony.

Samba dancers, capoeira performers and a drumming collective celebrated the vast South American country's rich cultural diversity as J.Lo and company sang the official World Cup song, "We Are One."

Excitement has built gradually in the days leading to the event, with increasing numbers of Brazilian flags flying from cars, bars and apartment blocks.

A giant Brazilian flag was draped at the foot of Rio's iconic Christ the Redeemer Statue on Thursday.

But while more Brazilians are sporting the yellow jersey of star forward Neymar, discontent continues to simmer.

The multi-billion-dollar cost of the World Cup has angered many in a country which has under-funded health and public services, and where violent crime is rampant.

Rage at poor public services morphed into a nationwide movement at the Confederations Cup test event, with deadly clashes rippling across the nation.

A vast security blanket is being deployed to shield the World Cup from unrest, with 150,000 soldiers and police on duty along with 20,000 private security officers.

Football's governing body FIFA begins the tournament under pressure over graft allegations linked to its decision to award the 2022 World Cup to Qatar.

FIFA secretary-general Jerome Valcke said that he was confident that after years of cajoling the organisers to speed up delivery of the stadiums, things were now ready.

"Overall the stadiums are ready," the 53-year-old Frenchman said. "Now it is more a problem of organisation than security."

For all the off-field problems, the tournament itself has the makings of a classic.

Reigning champions Spain are bidding to make history by becoming the first side from Europe to win a World Cup in South America, which last hosted the tournament in 1978.