London "designed a velvet revolution" to topple Iran's Islamic government and the detained staffers confessed to their role, he told the crowd, where some chanted slogans against the U.S. and Israel.

"In these events, their embassy had a presence," he said. "Some people were arrested. Well, inevitably, they will be put on trial."

He did not say how many staffers will be tried or on what charges. Earlier Iranian officials said all but one of the nine embassy personnel originally arrested had been released, but British officials say two are being held.

Government officials could not be reached on Friday for confirmation the staffers would be tried. Jannati does not hold a position in the government, but is the head of the Guardian Council, a powerful body in the 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."

Giant protests erupted in Tehran and other cities over the results, but they were put down in a tough crackdown after Khamenei declared unrest would no longer be tolerated. Police say 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.

In major cities across Iran, clerics delivering Friday prayer sermons told worshippers to accept the supreme leader's ruling on the results, according to transcripts on the state news agency IRNA.

In the northern city of Rasht, Ayatollah Zeinolabedeen Ghorbani said "anyone still saying they don't accept the results ... should be ashamed of themselves as a believer and a Muslim."

Jannati's message in his sermon was clear — that supreme leader Khamenei had guided the country out of the crisis. "A nation that has rule by the cleric (the supreme leader) and the law does not leave a problem unsolved," he told the crowd.

He indirectly accused Mousavi of treason, pointing 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."