Forty days after the death of Neda Soltan, the young Iranian woman whose harrowing last moments during a post-election protest were filmed and seen around the world, Tehran was the scene of extraordinary clashes yesterday as police used force to crush an opposition-backed memorial service for the student and other victims of violence.
Mirhossein Mousavi, the defeated presidential candidate and de facto opposition leader, was prevented by a phalanx of police from paying his respects at the grave of Ms Soltan, where large crowds had defiantly gathered for a ceremony to mark the 40th day since her death, a key moment of mourning in Shia Muslim tradition.
"Neda is alive! Ahmadinejad is dead!" many chanted as the tussle played out.
The other defeated candidate, Mehdi Karroubi, had to flee the cemetery after trying to deliver a speech near the grave while two leading Iranian film directors, one of whom was Jafar Panahi, nominated for an Oscar for one of his films, were arrested when they attempted to put flowers on the student's grave.
The demonstrations later spread to other parts of the Iranian capital with protesters chanting "Death to the dictatorship!", but police used batons and tear gas to charge the crowds and disperse them. Thousands had also assembled at the Grand Mosalla mosque, a key prayer venue, and other coordinated locations in the centre of the city, but police and security forces were posted in intimidating numbers at all the main intersections.
The heavy-handed response of the Islamic regime reflected a fierce determination to prevent mourning ceremonies for victims of post-election violence from turning into a vehicle for an unstoppable cycle of anti-regime protest.
Both sides would have been keenly aware that yesterday's events were laden with symbolism. Ms Soltan and 23 other slain protesters are buried in Behesht-e Zahra, the vast cemetery where, along with thousands who died during the 1979 revolution, thousands of soldiers "martyred" during the Iran-Iraq war are buried. The graveyard is one of the most important symbols of Iranians' suffering for independence. In 1977 and 1978, the forty day mourning ceremonies held there for anti-Shah protesters provided the monarch's opponents, under the guise of religious events, with a mechanism for huge demonstrations that eventually culminated in the revolution.
Yesterday's crackdown reflected both an intense fear within the regime's leadership of allowing history to repeat itself, analysts said, and a wish to scare off ordinary members of the public from coming onto the streets. "The regime is trying to demonstrate that it is not going to let even the smallest demonstration go ahead", said Dr Suzanne Maloney, of the Saban Centre for Middle East Policy at the Washington-based Brookings Institution. "Any political rally at the place where the martyrs of the revolution and the war are buried would have been an unthinkable challenge to the legitimacy of the regime".
The continuing difficulty for the regime however, she stressed, is that while it is willing to use enough force to deter casual followers from joining the protests, it will be difficult indefinitely to escalate force to put off the committed core of those now demanding political freedoms and even an end to the Islamic regime.
President Mahmoud Ahmadinejad is already facing a backlash from critics within the conservative political elite who are furious at his handling of the election and its aftermath.
"Clearly there are a large number of people in Iran who are willing to risk their safety to demonstrate. Force can keep a lid on this for a while but further deaths and an opposition leader with clear agenda for change would present a real problem for the regime," said Dr Maloney.
For opponents of President Ahadinejad, yesterday's defiance was an opportunity to demonstrate their refusal to accept his declared victory in the June 12 elections, or to be cowed into silence despite weeks of arrests, beatings, detentions, disappearances and the imminent threat of show trials of leading reformists.