Iranian reformist Mir Hossein Mousavi was given an ultimatum by the Islamic Republic's supreme leader Ayatollah Ali Khamenei in a call to support the reelected regime of President Mahmoud Ahmadinejad, the London Times reported Friday morning.

Opposition protesters take to the streets of Teheran

Khamenei made it clear to Mousavi that if he failed to report to Friday prayers at Teheran University, during which he planned to deliver a sermon calling for national unity, the oppostion leader would be exiled.

Khamenei is expected to be assisted by "an army of Islamic volunteer militiamen" during the sermon.

According the report, Khamenei made the demand while meeting with the representatives of candidates of the national elections that Mousavi had claimed were rigged.

On Thursday evening, hundreds of thousands of protesters wearing black and carrying candles filled the streets of Teheran, joining Mousavi to mourn demonstrators killed in clashes over Iran's disputed election.

The massive protest openly defied orders from Iran's supreme leader, despite a government attempt to placate Mousavi and his supporters by inviting the reformist, and two other candidates who ran against Ahmadinejad, to a meeting with the country's main electoral authority. Iran's Al-Alam Arabic television channel said the three candidates would meet with the Guardian Council on Saturday.

The council's spokesman, Abbasali Khadkhodaei, said Thursday that it received a total of 646 complaints from the three candidates who ran against Ahmadinejad in the June 12 election.

The council provided few other details, but the large number of complaints raised the possibility that even a limited recount could turn into a far larger and messier exercise than the government desires.

Many in the huge crowd carried black candles and lit them as night fell on Thursday. Others wore green wristbands and carried flowers in mourning as they filed into Imam Khomenei Square in the heart of the capital.

Press TV, an English-language version of Iranian state television designed for foreigners, estimated the crowd at hundreds of thousands and said the people listened to a brief address from Mousavi, who called for calm and self-restraint.

A Mousavi Web site said attendance exceeded 1 million.

Independent witnesses said that, based on previous demonstrations at the site, the size of the crowd appeared to be in the hundreds of thousands. The demonstrators had marched silently until they arrived at the square, where some chanted "Death to the dictator!"

Press TV showed protesters making V-for-victory gestures and holding pictures of Mousavi and signs that said "Where's our Vote?" A participant said by telephone that the rally stretched for more than 5 km. through downtown Teheran from the square.

Photos posted online showed Mousavi talking through a portable loudspeaker, dressed in a black suit and dark blue shirt as he raised a hand to address the massive crowd. The participant confirmed the authenticity of the images.

"A sea of people" marched across a bridge in a constant stream for three hours, he said.

"I remember one old man talking about how the will of the people has started and no one can stop it," he added.

On their way home, some demonstrators held a candlelit gathering in front of Teheran University, where Mousavi supporters have accused pro-government militia of attacking students in dormitories.

After dark Thursday - as they have done on other nights this week - people went to their roofs and chanted, "Mir Hossein!" in support of Mousavi, and "God is great!" Ahmadinejad released a largely conciliatory recorded statement on state TV, distancing himself from his past criticism of protesters, whom he has compared to angry soccer fans and "dust."

"I only addressed those who made riot, set fires and attacked people," the statement said. "Every single Iranian is valuable. The government is at everyone's service. We like everyone."

Israel continued to watch the Iranian situation closely from the sidelines on Thursday, saying it did not want to interfere in the Islamic republic's internal affairs, but was interested to see if the way the regime is dealing with the protests will impact on how the West, especially Europe, deals with the Iranian nuclear dossier.

Reflecting Israel's official policy, Foreign Minister Avigdor Lieberman said in Washington on Wednesday during his press conference with US Secretary of State Hillary Clinton that what united both front-runners in the Iranian presidential election was commitment to the country's nuclear program and a hatred of Israel.

What was important for Israel, he said, was not Iran's domestic problems, "but their policy. And we hope that they will change their policy."

The issue Israel is watching carefully, however, is whether the country's domestic problems will impact on that policy, or more immediately, whether the tactics the government is using to suppress the protesters will spur Europe into taking more stringent measures against the Iranian nuclear program.

On Monday, the 27 EU foreign ministers issued a statement that seemed to link the current developments and the nuclear issue.

"It remains a priority for the EU that Iran engages with the concerns of the world community, above all on the issue of Iran's nuclear program," the statement said. "The Council wishes to engage with the Islamic Republic of Iran on the basis of mutual respect, but it requires Iran to recognize and act urgently on its responsibilities and obligations."

Sources in Jerusalem said this was a rare case in which the EU was in any way hinting at a linkage between human rights issues and nuclear ones.