In Sweden, which currently holds the rotating EU presidency, Foreign Minister Carl Bildt said "it's not acceptable to file charges against the ones released or the ones still in custody," though he added that the report had not yet been confirmed.

On Thursday, EU countries demanded the release of the staffers, but held off on any sanctions for the time being. They took an further step Friday, summoning Iranian ambassadors across the 27-nation bloc in a joint protest over the arrests.

Jannati does not hold a position in the government or judiciary, but is the head of the Guardian Council, a powerful body in Iran's ruling clerical hierarchy that stands above the elected government.

The council oversees elections, and it carried out a partial recount which was ordered after Ahmadinejad's pro-reform rival Mir Hossein Mousavi cried fraud and said he was the victor. The recount ultimately upheld Ahmadinejad's election victory. Supreme leader Ayatollah Ali Khamenei declared the results would stand, and ruling clerics promptly called the elections "pure" and "healthy."

Iranian authorities have since depicted the widespread protests that erupted after the election as the work of outside enemies of Iran.

Jannati told the thousands of worshippers that the British "had designed a velvet revolution ... In March, they said (in their Foreign Ministry) that street riots were possible during June elections. These are signs ... revealed by themselves."

He also said those involved in protests "need to repent and ask God to forgive them."

Giant protests erupted in Tehran and other cities over the results, but they were quashed in a tough crackdown after Khamenei declared unrest would no longer be tolerated. Iran's police chief has said 20 "rioters" were killed during the violence. During his sermon, Jannati said seven or eight members of the paramilitary Basij militia were also killed. Basijis took a leading role in putting down the protests, often clashing with demonstrators.

There have been no street protests since Sunday, but Mousavi appears driven to maintain his opposition and even to raise the stakes. In a defiant statement on Wednesday, he said he considered the government illegitimate and demanded political prisoners be released. Still, he has been laying low, making no public appearances for days amid calls by many hard-liners for him to be prosecuted.

Jannati took a tough line, indirectly accusing Mousavi of treason.

Though he did not name Mousavi directly, Jannati pointed out that Ayatollah Ruhollah Khomeini, leader of Iran's 1979 Islamic revolution, once said that "anyone disrupts unity has not only committed a sin but also has committed treason against the Islamic Republic and the system."

Jannati demanded that those involved in the protests "repent and ask God to forgive them."

Keath reported from Cairo. Associated Press correspondent Ali Akbar Dareini in Tehran, Iran, contributed to this report.