The BBC's Jim Muir in Tehran reports on "the climax of eleven days of celebrations"

Helicopters showered the crowd with leaflets, soldiers parachuted in, and an army band played music in praise of the late Ayatollah Khomeini.

In a keynote speech, President Mohammad Khatami told the tens of thousands who had gathered in Azadi (Freedom) Square that the revolution remained strong despite the economic crisis caused by the collapse in oil prices.

The crowds converged on Freedom Square

He said Tehran would continue to seek massive foreign investment to help its recovery and called for an end to political feuding.

"The rule of law is our most important slogan in the period of the consolidation of the revolution and on the threshold of the third decade of the victory of the Islamic Revolution," President Khatami said.

Deep divisions

Thursday's ceremony marked the culmination of the "10-Day Dawn" commemoration of the events that ended 2,500 years of monarchy and established the world's first modern theocracy.

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Busloads of people converged on the capital from outlying towns and suburbs to take part in the biggest of the anniversary demonstrations called by the authorities.

Correspondents say the rally also served to smooth over the deep division between the reformists and the traditionalists which strikes at the heart of Iranian society.

Public holiday

Tehran centre was closed off to traffic allowing six large processions to set off from different points around the capital towards Freedom Square.

Each year the authorities galvanise thousands for the main rally, but this year the Islamic authorities had called for an even larger turnout than usual.

The republic's supreme leader, Ayatollah Ali Khamenei, had urged Iranians to attend. He said: "Every year the revolution's enemies look carefully to see whether people will participate. Let people show them their continued support the revolution with their overwhelming presence."

Revolutionary reminder

In the past two weeks, state radio has broadcast a selection of old revolutionary songs, designed to remind Iranians of the heady days of the 1979 revolution.

But the government has been forced to acknowledge the mounting problems faced by ordinary people as a collapse in the value of Iran's main export oil has led to a worsening economic crisis.

"Among the major problems facing the country today are unemployment, inflation, financial corruption, nepotism, favouritism and, above all, the lack of expert plans for developing the country's enormous potential," the English-language Tehran Times said on Wednesday.