BBC News
President Mahmoud Ahmadinejad said opposition groups who worked against the regime would be “banished by the people”.
Supreme Leader Ayatollah Ali Khamenei also gave a warning to past leaders now considered opposition figures.
Tens of thousands gathered at a shrine to mark the death 21 years ago of revolution leader Ayatollah Khomeini.
Ayatollah Khomeini led the 1979 revolution which toppled the US-backed Shah of Iran.
The rally comes just days before the anniversary of last year’s disputed elections.
Past record
Ayatollah Khamenei said Iran was in a position to “see off any conspiracies.”
He said people would be judged by their current actions, not their past record.
The BBC’s Jon Leyne says this is an apparent warning to the opposition leadership, which includes a former president and prime minister.
Opposition candidates claimed President Ahmadinejad changed the result of last June’s election.
There were mass rallies to protest and thousands of opposition supporters were arrested.
Dozens were killed in clashes with police and at least nine have been sentenced to death following the protests.
The grandson of Ayatollah Khomeini was interrupted by the crowd when he tried to speak at Friday’s rally.
Hassan Khomeini is perceived by some to support opposition leaders.
President Ahmadinejad also condemned a raid by Israeli commandos on ships trying to take aid to Gaza.
He said “thousands of flotillas” would follow them.
