CBN radio and the website of the Estado de Sao Paulo newspaper, both respected, mainstream media, carried reports speculating that the eight-team tournament, considered a dry run for next year's World Cup, was in danger.
"FIFA will claim compensation from Brazil if the Confederations Cup has to be suspended," said a headline on CBN's website.
An estimated one million people took to the streets in cities across Brazil on Thursday as the country's biggest protests in two decades intensified despite government concessions meant to quell them.
"On the legal side, there's a certain degree of confidence on FIFA's part that if the tournament is cancelled, it can launch a claim from the Brazilian government, if there are no safety guarantees for the competition or the World Cup," said the report by Juck Kfouri, a veteran Brazilian sports journalist.
"There is strong speculation, which won't go away," he added, referring to rumours that the competition was in danger.
"The protests in the streets of Brazilian cities have forced FIFA to negotiate with the teams to keep them in the Confederations Cup," it said.
"By law, if there is no guarantee of safety, it could force the tournament to be cancelled."
The Folha de Sao Paulo said that FIFA and the participating teams were "terrified" by the situation.
"The competition has become a nightmare for the organisation," it said. "FIFA didn't imagine that the event would be perfect but the size of the problems is worse than the worst-case scenario."
