Iranian opposition leader calls for rally Thursday

Iranian opposition leader Mir Hossein Mousavi issued a direct challenge on Wednesday to the country's supreme leader and cleric-led system, calling for a mass rally to protest disputed election results and violence against his followers.

A crackdown on dissent continued, with more arrests of opposition figures reported, and the country's most powerful military force -- the Revolutionary Guard -- saying that Iranian websites and bloggers must remove any materials that "create tension" or face legal action.

Supreme Leader Ayatollah Ali Khamenei has told Mousavi to pursue his demands through the electoral system and called for Iranians to unite behind their Islamic government, an extraordinary appeal in response to tensions over the presidential vote. But Mousavi appears unwilling to back down, issuing on his website a call for a mass demonstration Thursday.

"We want a peaceful rally to protest the unhealthy trend of the election and realize our goal of annulling the results," Mousavi said.

He called for "a new presidential election that will not repeat the shameful fraud from the previous election."

Websites associated with Mousavi and the reformists called for at least one rally later Wednesday but the opposition leader made no reference to the gathering in his official statement.

Mousavi and his supporters accuse the government of rigging the June 12 election to declare hard-line President Mahmoud Ahmadinejad the overwhelming winner.

Their street protests, paired with dissent from powerful clerical and political figures, have presented one of the gravest threats to Iran's complex blend of democracy and religious authority since the system emerged from the 1979 Islamic Revolution.

Blogs and websites such as Facebook and Twitter have been vital conduits for Iranians to inform the world about protests and violence.