In a speech before a crowd at Tehran University, Ayatollah Khamenei warned protestors of last week's presidential vote that they will face a stiff reaction from authorities if they do not show restraint.

The supreme leader passionately defended the election of President Mahmoud Ahmadinejad, calling it a"definitive victory" and dismissing charges of vote tampering.

Protestors have staged noisy demonstrations for the last six days to dispute what they believed was a rigged election.

Khamenei called on these individuals to use proper legal avenues, such as requesting a recount, but did not himself issue a call for a new vote.

Despite threats of punishment, more protest rallies are planned for Saturday.

Amnesty International issued a statement on Friday saying Khamenei's sermon "indicates the authorities' readiness to launch violent crackdowns if people continue to protest which may cause a widespread loss of life."

Want to know more about the history behind the conflict? Check out our Iran's 'Twitter Revolution' article.