Demonstrators near the Eiffel Tower in Paris Wednesday protest the outcome of the presidential election in Iran. The clerical government in Iran appears to be trying to defuse popular anger and quash unrest by announcing a limited recount even as it cracks down on foreign media and shows its strength by calling supporters to the streets.

TEHRAN, Iran — Opposition leader Mir Hossein Mousavi called his followers back into the streets of Tehran today for another rally over Iran's disputed presidential election and urged them to wear black to mourn those killed in clashes.

The call for opponents of President Mahmoud Ahmadinejad to rally again was in open defiance of the country's supreme leader, who has urged the nation to unite behind the Islamic state. It came a day after tens of thousands marched silently down a main street of the capital, brandishing posters of Mousavi and waving V-for-victory signs, amateur video showed. Some covered their mouths with masks.

International news organizations have been banned from covering the protests over last Friday's election, which the government declared hard-line President Mahmoud Ahmadinejad won by a landslide. Mousavi and his supporters claim the election was rigged and he was the winner.

On Monday, hundreds of thousands turned out in a huge procession that recalled the scale of protests during the 1979 Islamic Revolution. Seven demonstrators were shot and killed that day by pro-regime militia in the first confirmed deaths during the unrest.

Mousavi's Web site said he may join the rally today in downtown Tehran. The protest would be the fourth straight day of major marches in the capital — rallies that recalled the unrest three decades ago that brought down Western-backed Shah Mohammad Reza Pahlavi and propelled the Islamic clergy to power.

The street protests have presented one of the gravest threats to Iran's complex blend of democracy and religious authority since the system emerged out of the Islamic revolution. But the chances of bringing down the Islamic system appear remote. The ruling clerics still command deep public support and are defended by Iran's most powerful military force — the Revolutionary Guard — as well as a vast network of militias.

But Mousavi's opposition movement has forced the country's supreme leader, Ayatollah Ali Khamenei, into the center of the escalating crisis, questioning his role as the final authority on all critical issues.

Iran's main electoral authority has said it was prepared to conduct a limited recount of ballots at sites where candidates claim irregularities. The recount would be overseen by the Guardian Council, an unelected body of 12 clerics and Islamic law experts close to Khamenei. Mousavi alleges the Guardian Council is not neutral and has already indicated it supports Ahmadinejad. He wants an independent investigation.

Today, state radio reported that the council has invited Mousavi and two other candidates who ran against Ahmadinejad to a meeting early next week. It did not say exactly when or where the meeting would take place.

Another pivotal figure in the escalating drama is former President Hashemi Rafsanjani, who heads the Assembly of Experts — a cleric-run body that is empowered to dismiss the supreme leader. Rafsanjani was a fierce critic of Ahmadinejad during the election, but has not publicly backed Mousavi.

For the moment, protesters have focused on the results of the balloting rather than challenging the Islamic system of government.

But a shift in anger toward Iran's non-elected theocracy would sharply change the stakes. Instead of a clash over the June 12 election results, it would become a showdown over the foundation of Iran's system of rule — the almost unlimited authority of the clerics at the top.