TEHRAN  Iranians angry at the results of last week’s election pushed their protest forward on Wednesday, from tens of thousands who again flooded the streets here to six soccer players on the national team who wore opposition green wristbands at a World Cup qualifying game.

But there were signs of an intensified crackdown: The government worked on many fronts to shield the outside world’s view of the unrest, banning coverage of the demonstrations, arresting journalists, threatening bloggers and trying to block Web sites like Facebook and Twitter, which have become vital outlets for information about the rising confrontation here.

The senior prosecutor in the central province of Isfahan, where there have also been tense demonstrations, went so far as to say protesters could be executed under Islamic law.

As nations around the world urged Iran’s leadership to exercise restraint, Mir Hussein Moussavi, the opposition presidential candidate who the government said finished second, and one of Iran’s chief reformers, Mohammad Khatami, issued a joint letter urging an end to violence and arrests.