Tehran's crackdown on opposition protests has earned it condemnation from international powers
Tens of thousands of protesters have taken to the streets across Iran for a series of state-sponsored rallies designed as a show of strength following days of pro-opposition demonstrations.
State television footage showed crowds in areas including Tehran's Enghelab Square, chanting slogans and waving pro-regime placards.
The government gave all civil servants and employees a day off to attend the rallies and organised buses to transport groups of schoolchildren and supporters from outlying rural areas to the protests.
Demonstrators at a rally in Tehran chanted "Death to Mousavi," a reference to opposition leader Mir Hossein Mousavi.
Some shouted "Rioter hypocrites must be executed" and held up a banner that read: "We sacrifice our blood for the supreme leader."
The state news agency IRNA said that the two senior leaders of the opposition, Mir Hossein Mousavi and Mehdi Karroubi, had fled Tehran on Wednesday, while a website said they were in custody for their own protection.
"Two of the chiefs of the sedition left Tehran for the north of Iran after learning that the population was increasingly angry and demanding their punishment," IRNA said.
Opposition website Rahesabz said "members of the Revolutionary Guards and the intelligence ministry picked up Mousavi and Karroubi in the city of Kelar-Abad to protect them from the anger of the people."
A top aid to Mousavi, however, denied the reports, telling Al Jazeera that "Mousavi is in Tehran."