President Mahmoud Ahmadinejad on Tuesday made his first televised address since Iran’s disputed elections, calling them “the freest” and “healthiest” in the world, while opposition leaders seeking to revitalize their movement demanded an end to the government crackdown and the release of hundreds of arrested protesters.

Faced with rising clerical and political opposition, Mr. Ahmadinejad tried to rally support for a second term whose legitimacy has been questioned before it has even begun, adopting conciliatory language even as his allies in the security services worked to extinguish the burning embers of opposition by force.

Despite the crushing of its street protests, the opposition vowed to continue its movement against what it calls a fraudulent election, planning major rallies in three cities on Thursday, which the government already appeared to be trying to derail.

The defeated presidential candidates Mir Hossein Moussavi and Mehdi Karroubi and former President Mohammad Khatami issued a joint statement late Monday demanding an end to the crackdown, in which hundreds of political figures, intellectuals, journalists and demonstrators have been detained since the June 12 election.