Opposition supporters defied warnings from the authorities to protest
By Jim Muir
Former BBC Tehran correspondent
The clashes and arrests that marked Friday's Qud's (Jerusalem) Day marches have underlined once again how deep and unresolved the crisis and divisions in Iran remain, more than three months after the disputed re-election of President Mahmoud Ahmadinejad.
In the face of severe repression, the opposition movement had not been able to stage any show of strength on the streets for two full months.
The protest turnout on Friday, defying warnings from the hardline authorities, showed that the movement is still alive and willing to take risks to show it is still in contention.
But qualitatively, it produced nothing new, and the scale was considerably smaller than the massive displays of outrage that came in the early days after the announcement of Mr Ahmadinejad's huge official margin of victory.
If opposition leaders are now asking themselves what they can do for an encore, the system loyalists also face a dilemma about how far to go in curbing the continuing defiance.
With prominent leaders such as Mir Hossein Mousavi, Mehdi Karroubi and Mohammad Khatami joining the rallies despite official warnings, and the rank and file willing to risk being beaten and arrested, the flames of revolt are clearly still there.
Reports of disturbances in other provincial cities must also have stirred alarm.
One possible course open to the hardline authorities might be to detain the top-ranking opposition leaders and put them behind bars on sedition charges.
There have been intensifying calls for such action in right-wing circles, and predictions from liberal sources that that might usher in the next phase of the struggle.
The latest unrest came at a bad time for Mr Ahmadinejad and the hardliners, including the Supreme Leader, Ayatollah Ali Khamenei.
Mr Ahmadinejad said combating Israel was a religious duty for Muslims
It made the country look unstable, and the president's authority challenged from within, as he was preparing to travel to New York to address the United Nations General Assembly next week.
Iran is also set to hold groundbreaking talks with the five permanent members of the UN Security Council and Germany, to discuss their mutual concerns - and particularly, Western suspicions that Iran is working towards an atomic bomb through its pursuit of the nuclear fuel cycle.
In advance of those important encounters with the outside world, Mr Ahmadinejad used the Jerusalem Day occasion to strike the kind of strident posture that is unlikely to give him a warm reception among some of those assembled at the UN in New York next week.
Once again, and unambiguously, he dismissed the Holocaust as a myth, and he repeated that combating Israel was a religious and national duty for Muslims.
US President Barack Obama's decision to move away from his predecessor's plans for a land-based missile system in Eastern Europe to counter a perceived threat from long-range Iranian missiles might be seen as an element favouring detente between Tehran and Washington, which will be playing a full part in the 1 October talks with Iran for the first time.
But it may have a negative effect from Iran's viewpoint, by making Russia more vulnerable and responsive to pressures to take a tougher line with Iran over its nuclear programme.
Events of the past few months in Iran - including the continuing crackdown involving the detention and "confessions" of liberal figures - have reinforced the conclusion of some analysts that what has happened is an internal hardline quasi-military coup which has disturbed a balance that had characterised the Islamic system in Iran from the outset.
Some theorists have speculated that the lurch may have been triggered inadvertently by Mr Obama's outstretched hand, prompting the hardliners to conclude that their vision of the system could not survive the social, cultural and political implications of normalisation with the US and the Western world.
That theory will be tested fully in the coming months, which will either see a movement towards rapprochement, or a hardening of positions that could lead to tougher international sanctions on Iran, and possibly even eventual military action.