As soon as the referee blows the final whistle he is surrounded by riot police on the pitch who stop players, coaches and even reporters from getting close enough to question or criticise his performance.

This is a recurring image at Brazilian soccer matches with riot police ever present at stadiums, as is the violence that marred Wednesday night's Copa Sudamericana final in Sao Paulo, one of the cities that will host the 2014 World Cup finals.

Modest Argentine side Tigre accused police and Sao Paulo security officials of attacking and pulling guns on their players in their dressing room at halftime in the Morumbi where they were 2-0 down to the home side and refused to play the second half.

The first half had ended in a free-for-all involving players and officials of both teams as they left the pitch and police also fought with about 60 Sao Paulo fans who invaded the pitch to celebrate when the referee declared their team winners.

"Of course we have no jurisdiction over this match but it is not a good image for Brazil and it must change," Ricardo Trade, CEO of Brazil's World Cup organising committee, told reporters on Thursday.

"Those kinds of TV pictures are not good for us, we don't want them of course," he said during a tour of World Cup venues.

"We also want to change another negative image, of the military police in the stadiums and escorting the referee and officials off at the end. It is not a positive image.

"We will not have this at the World Cup. The regular stewards will escort the referee and while the military police will be in the stadium they will not be seen... unless something happens that they need to deal with."

A strong police presence in stadiums was the government's response to violent hooligan fans on the terraces in the 1980s that only worsened in the 1990s.

Rio de Janeiro authorities, appalled by mass brawls on the terraces at the giant Maracana stadium during major derbies, created a police unit in 1991 specially trained for soccer matches bearing firearms with mounted patrols outside the grounds that are being reformed for the World Cup.

There has been some success in controlling soccer hooligans with fighting occurring some distance from the stadiums on match days but the police presence merely results in fighting, tear gas and arrests at matches.

Another recent incident of police intervention at a match in Brazil involved former Real Madrid and Brazil coach Vanderlei Luxemburgo, now in charge of first division Gremio.

Police escorted Luxemburgo from the field after the referee ordered him off for protesting his decisions during the Porto Alegre derby against Internacional on the last day of the Brazilian championship earlier this month.

It is not only police, however, who tarnish the image of Brazil, who will host the World Cup finals for the second time.

Dozens of people with some link to the teams follow matches from the edge of the pitch with invasions commonplace to celebrate a goal or protest a refereeing decision - leading to police also coming onto the field.

There is also a big media presence pitch-side with television and radio reporters poised to run onto the pitch for a quick interview at any time during a match.

Former Brazil goalkeeper and coach Emerson Leao and three players of Goias, the team he was training in 2010, were taken to a police station after attacking a radio reporter who approached them at the end of a game against Vitoria.

The World Cup looks like an opportunity for change for Brazil.

"We hope that after the World Cup, too, we will not see police surrounding the officials at the end of the game... It sends the wrong image," said Trade.

"We are working on it."