Furious Croatia coach Niko Kovac blamed "out of his depth" referee Yuichi Nishimura and warned the World Cup could turn into a circus after a contentious penalty decision effectively cost his team the opening game of the tournament against Brazil.

Japanese ref Nishimura ruled that Dejan Lovren had fouled Fred when the Brazilian fell to the floor at 1-1 with 20 minutes remaining and the score at 1-1. Neymar converted the penalty for his second goal of the game and they went on to win 3-1 in Thursday's Group A match.

“This was ridiculous today, and if we continue in this way we will have a circus,” Kovac said after the match.

“If that’s a penalty, we don’t need to play football any more. Let’s play basketball instead. 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, who said his team deserved at least a draw from a match played at a packed Corinthians arena in Sao Paulo, also felt Oscar’s third goal near the end of the game should not have been allowed due to a foul earlier in the move.

“Was there a foul on my player? Yes. It was a foul. But that’s life. We will march on. We will not be swayed.”

Kovac, stony-faced yet calm, praised his team, which took the lead in the 11th minute after an own goal by Marcelo, and had several scoring chances during the rest of the match.

"My lads have fought for two years to reach the World Cup. They worked hard, prepared, and then they were faced with such a penalty decision here. You can imagine walking into our dressing room - what kind of mood my lads are in."

Kovac said he did not blame Fred for his theatrical fall. “The referee was well-placed, he was not unsighted, he saw everything and he took that decision,” he said. “I don’t blame Fred at all.”

Croatia’s fans were also furious with the Japanese official.

“I’ll never eat sushi again,” said Goran, a Croatian fan who attended the game as he ate dinner afterward. “I guess the world was against us today.”

Brazil coach Luiz Felipe Scolari rejected claims they were favoured by the referee and heaped praise on Neymar.

Scolari said his team showed great character after bouncing back from an early own goal and singled out 22-year-old Neymar for his man of the match performance.

“The only thing we want is that Neymar is happy playing ball. He’s a special player,” Scolari said.

Scolari responded to Kovac’s comments by reminding him that Brazil has won the World Cup more times than any country and did it without any help from referees.

“I’m not going to comment on what my colleague (Kovac) said. The only comment I can make is that Brazil has five World Cup titles,” he said.

“Those weren’t five circuses in favor of Brazil. The referee saw a penalty. It’s the referee that has to decide.”