* Neymar double helps hosts recover to beat Croatia 3-1
* Brazil recover from early Marcelo own goal to triumph
* Japanese referee awards home side controversial penalty
By Peter Rutherford
SAO PAULO, June 12 (Reuters) - Seven years a hostage to threats of violent demonstrations and crippling labour strikes, the World Cup broke free on Thursday when Brazil brought the tournament to life with Neymar scoring twice in a thrilling 3-1 win over Croatia.
It was far from vintage Brazil at times, impatient in possession and unsure in defence, but once they hit full stride they were impossible to resist - the inimitable Neymar and ebullient Oscar taking the game by the scruff of the neck.
After falling behind to an 11th minute own goal from unfortunate defender Marcelo, forward Neymar equalised with a terrific strike from outside the box before converting the softest of penalties late in the second half.
Midfielder Oscar capped an outstanding performance with a goal of true quality in stoppage time that sealed the three points for Brazil and brought an enormous roar of relief from the 62,103 crowd at Sao Paulo's Corinthians arena.
For 22-year-old Neymar, scoring twice on a night when the World Cup returned to the spiritual home of football was beyond his wildest dreams.
"I'm very happy, really happy indeed, more than I ever dreamed or imagined," the man of the match told reporters.
"We started off on the right foot, with a victory.
"The merit belongs to the team as a whole, which remained cool and calm to come from behind and win."
And how the home fans revelled in the win. A delirious, dancing sea of yellow hailing the victory as the first step towards a record-extending sixth World Cup title.
The buildup to this World Cup has been tarnished like no other, with simmering public anger over the $11 billion spent on construction projects while much of the country struggles to keep itself out of poverty boiling over on to Brazil's streets.
Scattered violent protests before the game were a reminder that many locals remain frustrated over the billions spent to host the tournament, but for 90 special minutes it was football's chance to shine.
In the wake of the embarrassing, hostile reception from fans at last year's Confederations Cup, Brazil President Dilma Rousseff and FIFA chief Sepp Blatter chose not to address the opening ceremony.
But the supporters made their feelings clear about the lack of investment in social infrastructure in Brazil, directing obscene chants at President Rousseff during the game and booing loudly when she was seen celebrating the goals on the stadium screens.
Winning the World Cup on hallowed, home soil would no doubt go some way to soothing some of Brazil's wounds and the Selecao are now six more wins away from achieving that.
Croatia clearly had not read the script and, after forward Ivica Olic headed narrowly wide, they took the lead in the 11th minute through Brazil's first ever World Cup own goal.
Olic's low cross from the left went through the legs of Brazil skipper Thiago Silva, clipped Nikica Jelavic's foot and bounced in off Marcelo with keeper Julio Cesar left helpless.
A moment's stunned silence was quickly replaced by chants of "Brazil! Brazil!" as the crowd pleaded with the home side to strike back quickly.
Inevitably it would be Neymar who answered their prayers.
He marked his 50th appearance for Brazil with a superb equaliser in the 29th minute, dragging a low shot into the corner of the net past the despairing dive of Stipe Pletikosa.
Neymar's 33rd international goal arrived in more controversial circumstances after Japanese referee Yuichi Nishimura awarded the home side a 71st-minute penalty.
Brazil striker Fred fell to the ground under the slightest contact from Dejan Lovren and, after Nishimura pointed to the spot, the referee was surrounded by furious Croatian players questioning the call.
Once the dust had settled, Neymar kept his cool to stroke the penalty home.
Croatia coach Niko Kovac warned that the World Cup could become a "circus" after Nishimura's decision.
"This was ridiculous today, and if we continue in this way we will have a circus," he told reporters at a post-match news conference dominated by questions about the spot kick.
"If that's a penalty, we don't need to play football any more. The lads played their hearts out but that was outright thuggery by a referee who was just out of his depth for a game of this magnitude."
Kovac's Brazil counterpart, Luiz Felipe Scolari, did not agree with his counterpart's thoughts on the contentious award.
"I'm not going to comment on what my colleague said. The only comment I can make is that Brazil has 5 World Cup titles. Those weren't five circuses in favour of Brazil.
"I perfectly understand my colleague's remarks, and I respect them ... But I don't see any favouring of Brazil in those five World Cup titles."
While debate about the penalty will continue long after Thursday's game, there was no doubting the class of Oscar's strike that wrapped up Brazil's win.
Bursting clear of the tiring Croatia defence in stoppage time, he toe-poked the ball home to seal Brazil's 10th successive victory and give them the perfect start to their World Cup campaign. (Editing by Ken Ferris)