The Interior Ministry of Iran yesterday declared such a gathering illegal, leading to reports that a rally in support of Mir-Hossein Mousavi would be postponed or canceled.

But it went forward, with plenty in attendance to protest Friday's rigged elections, which pronounced Khameini-backed Mahmoud Ahmadinejad winner by a margin of 2-to-1.

"The street is fully packed," the witness said, adding the crowd was waiting for Mousavi and other pro-reform leaders who back his call for the annulment of the official result of Friday's election, which showed President Mahmoud Ahmadinejad had won.

Wearing Mousavi's green campaign colors and photographs of him, they chanted: "Mousavi take back our votes."

Several kilometers of a central Tehran thoroughfare were packed with people taking part in the rally, the witness said.

"Where are the 63 percent who voted for Ahmadinejad?" they chanted, referring to his official election tally.

"If Ahmadinejad remains president we will protest every day," they shouted. "We fight, we die, we will not accept this vote rigging," was another chant in the crowd.

As a police helicopter flew overhead, the crowd booed.

Meanwhile, supreme leader Khameini, finding himself on the wrong side of the public outrage, has flip-flopped and ordered an investigation of the election results.

State television quoted Ayatollah Ali Khamenei directing a high-level clerical panel, the Guardian Council, to look into charges by pro-reform candidate Mir Hossein Mousavi, who has said he is the rightful winner of Friday's presidential election.

The decision comes after Mousavi wrote a letter appealing to the Guardian Council and met Sunday with Khamenei, who holds almost limitless power over Iranian affairs. Such an election probe by the 12-member council is uncharted territory and it not immediately clear how it would proceed or how long it would take.

Khameini had previously released a statement- his first comment on election results ever-praising Ahmadinejad's victory, but Amir Taheri thought it rung untrue:

This was the first time since 1989, when he became supreme leader, that Mr. Khamenei commented on the results of a presidential election without waiting for the publication of official results. Some analysts in Tehran tell me that the military-security elite, now controlling the machinery of the Iranian state, persuaded Mr. Khamenei to make the unprecedented move.

A detailed study of Mr. Khamenei's text reveals a number of anomalies. It is longer than his usual statements and full of expressions that he has never used before. The praise he showers on Mr. Ahmadinejad is simply too much. The question arises: Did someone use the supreme leader as a rubber stamp for a text written by Mr. Ahmadinejad himself?

Meanwhile, Iranian dissidents and their supporters wonder, "Where is Obama?"

The Wall Street Journal urges him to act on behalf of the protesters:

Having shown such courage, the demonstrators deserve Western support, not least from the media that have recently trumpeted the Mousavi candidacy as evidence of Iran's openness and potential for reform, conciliation and so on. Whatever happens in the days ahead, the world has now seen the tyranny raw. The least we owe the protestors is not to look away.