4:44pm UK, Monday June 15, 2009

Tens of thousands of a defeated presidential candidate’s supporters have gathered in Tehran – defying an Iranian interior ministry ban.

Riot police line up before Mousavi supporters in Tehran

Mirhossein Mousavi is calling for the annulment of Friday’s election result, complaining of vote-rigging.

Official figures showed hardliner President Mahmoud Ahmadinejad – who denies the claims – had beaten him by a landslide.

Thousands protest in the capital

Since the result, there has been three days of demonstrations, some involving violent clashes between protesters and police.

Mr Mousavi has reportedly joined the masses at the latest rally, despite an interior ministry warning that such a gathering would be illegal.

Reports said the country’s supreme commander Ayatollah Ali Khamenei has called on the Guardian Council – a 12-member body that is a pillar of Iran’s theocracy – to examine the vote-rigging claims.

Violence at a protest on Sunday

Meanwhile, Tehran is facing a growing international backlash over the validity of the election and the subsequent crackdown on opposition protests.

Mr Ahmadinejad has defended the results of a vote that gave the combative hardline another four years in power.

His victory dented Western hopes of a change in domestic and foreign policy of the oil-rich Shiite-dominated nation.

As riot police looked on, demonstrators continued to stream into central Tehran, raising the possibility of tense confrontations.

The latest opposition protest comes a day after Mr Ahmadinejad himself addressed a victory rally of vast crowds of supporters in Tehran to defend the results.

“Elections in Iran are the cleanest,” he said. “Today, we should appreciate the great triumph of the people of Iran against the united front of all the world arrogance (the West) and the psychological war launched by the enemy.”

The authorities have warned that they would crush any “velvet revolution” in Iran and police said they have rounded up 170 people over the protests, including a number of reformist leaders.