The famously grumpy coach also held Saturday's practice behind closed doors after the media reported a flare-up between Dani Alves and Julio Baptista in a previous training session.
Dunga's decision is almost unprecedented for the Brazilian team, where radio and even television stations carry live broadcasts of training sessions in the run-up to important games and tournaments.
Team spokesman Rodrigo Paiva appeared as frustrated as anyone.
"Before the World Cup, we put forward plans as to how we would work but it's the coach who decides whether or not we put it into practice," he said.
Dunga's unhappy relationship with the media goes back to the 1990 World Cup when, as a player, he was made the scapegoat for the team's poor display which ended in a second-round exit at the hands of Argentina.
Dunga's approach, based on tough tackling and work rate, was seen as symbolic of the way in which the team had changed from the traditional Brazilian attacking style to a more European one.
It was named the Dunga Era.
Four years later, Dunga bounced back when he captained the team which won Brazil's fourth World Cup title, ending a 24-year wait.
Shortly after Brazil arrived in South Africa, Dunga claimed that there were 300 reporters present who wanted the team to lose.
Midfielder Ramires, who plays for Benfica, said the players supported the move.
"It's like that in Portugal, sometimes you just see the players having a jog, sometimes not even that," he said. "I think it helps a lot.
"It means the opposition knows less about our team."
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