The momentum of Iran's "green revolution" - triggered by allegations of electoral theft earlier this month - appeared to stall today, as thousands of plain clothes and uniformed security officials swamped Tehran, using tear gas and water cannon on a hard core of about 3,000 demonstrators.
The latest clashes on Tehran's streets came as defeated presidential candidate Mir Hossein Mousavi released a letter he had sent to the Guardian Council - Iran's top legislative body - insisting that the results of the election be annulled and claiming that a plan to rig the 12 June poll in favour of Mahmoud Ahmadinejad had been planned months in advance.
Eyewitnesses said that protesters who had tried to gather for demonstrations were beaten by police, who also fired warning shots into the air. Video footage showed scattered knots of protesters fleeing as tear gas canisters were fired amidst shouts of "Allahu Akbar" - God is Great, one of the calls adopted by the protesters.
In other places, witnesses described demonstrators holding their ground against motorbike-mounted members of the feared Basij militia.
Helicopters hovered over Tehran and the sound of sirens echoed through the streets as up to 60 injured demonstrators were taken to the Imam Khomeini hospital. Tehran's university campus - another focal point for the protesters - was also blocked off by lines of police. Supporters of Mousavi were rumoured to have set fire to a building in southern Tehran used by Ahmadinejad supporters.
"This is like [the revolution in] 1979," said one older man on the streets. "But it's more dangerous. People had money in 1979 to escape and to get by for months. Now they don't."
After stern warnings from Iran's supreme leader Ayatollah Ali Khamenei during Friday prayers and amid a climate of growing fear in Iran, the vast majority of the hundreds of thousands who had earlier marched against what they claimed has been the rigging of elections to favour Ahmadinejad, appeared to have remained at home. Khamenei warned opposition leaders to end street protests or be held responsible for any "bloodshed and chaos" to come.
The protests have been the most serious challenge to Iran's clerical regime since the Islamic Revolution in 1979 that saw the downfall of the Shah.
Clashes between police and protesters chanting "death to the dictator" came as the Guardian Council announced it was ready to re-count a random selection of a tenth of the votes from the disputed presidential poll.
Mousavi and Mehdi Karoubi, another defeated candidate, refused to attend the meeting with the Guardian Council to discuss the 646 complaints of voting irregularities.
Ordinary Iranians, as well as observers both inside and outside Iran, are now waiting for Mousavi's next move. The man who has become the focal point for challenges to the regime appears to have stepped back from open confrontation in the past two days.
In a sign of the regime's determination to prevent further large protests, police and Basij militia deployed in almost every major square in Tehran, while fire engines were being used to block roads, eyewitnesses said. One told al-Jazeera that in most areas protesters were outnumbered by riot police. Ahmad Reza Radan, a senior Iranian police commander, had warned his men would "strongly confront any illegal gatherings and those without permission".
In the first indications that the extraordinary week of protests might be coming to an end, Karoubi's Etemad-e Melli party said plans for their participation in the rally had been scrapped for lack of a permit. "Because of not obtaining permission, the rally today has been cancelled," a party spokesman said. An ally of Mousavi said the politician had urged his supporters not to march on Saturday or Sunday.
The clashes in Enghelab Square came as Iranian state television reported that a bomb had exploded at the Tehran shrine of Ayatollah Ruhollah Khomeini - the father of the country's Islamic revolution - wounding two people, an act that could be used to justify a wider crackdown. Reports of the bombing could not be independently confirmed. Last week Iranian authorities said they had uncovered plans to bomb mosques during the election period.
Up to 10 people have been killed and scores of reformists have been arrested since the protests began. Authorities have also cracked down on foreign and domestic media.
The violent interventions of the Basij militia - one of Ahmadinejad's bases of electoral support - armed with bicycle chains, batons and Kalashnikovs and dressed in a mixture of civilian clothes and fatigues, is an increasingly significant factor in the crisis.
Special units of the Army of Mohammad Rasulallah, part of the Revolutionary Guard noted for its iron fist tactics, have also reportedly taken over law enforcement in the capital. The Basij is a volunteer force, drawn mainly from the poorer section of society, who gain favours and privileges by acting as enforcers for the Islamic state. The pressure opposition leaders now feel contrasts with the mood earlier in the week when young men and women with green ribbons around their wrists had proudly said, "We're not afraid". Now everyone knew the stakes had been raised.
"Everyone is frightened now," said a young man who had been out on the streets every day since the election. "I just can't talk you. I can't say anything now," said an aide to Karoubi.
Whatever happens in the weeks and months that follow, the events of the past 10 days have shaken the Islamic Republic. The Guardian Council approved the four presidential candidates, believing that none would pose any danger to the system, but the refusal of so many millions of people to accept the result took the authorities by surprise. Mousavi, a conservative by nature, has frequently appeared to be following the protestors rather than leading them, and it is not clear that he can satisfy them if he opts to try compromise rather than continued confrontation.
"The revolution is a strong ship which did not falter in the storm," said Khamenei. It is far from clear whether the storm has passed.
• Lindsey Hilsum is International Editor of Channel 4 News
Auch eine Woche nach dem Ausbruch der Proteste hält der Widerstand gegen das Ergebnis der Präsidentschaftswahl vom 12. Juni 2009 an. Am Freitag hatte der religiöse Führer und Staatsoberhaupt Ali Chamenei in einer Rede die Zweifel an dem Wahlergebnis zurückgewiesen und die Anhänger der unterlegenen Kandidaten deutlich vor weiteren Demonstrationen gewarnt. Im Zentrum der iranischen Hauptstadt ging die Polizei mit Tränengas und Wasserwerfern vor, teilweise knüppelten die Einsatzkräfte mit Schlagstöcken auf etwa 3.000 Demonstranten ein. Es sollen auch Warnschüsse gefallen sein. Berichten zufolge wurden bis zu 60 Verletzte Demonstranten in das Imam-Chomeini-Krankenhaus gebracht. Seit Beginn der Proteste wurden mindestens zehn Personen getötet, Menschenrechtsorganisationen zufolge bis zu dreißig.

Das Innenministerium hat Demonstrationen im ganzen Land verboten und die Polizei erklärte, „von sofort an hart und entschlossen“ vorgehen zu wollen. Zehntausende von Polizisten und Revolutionsgardisten waren am Samstag in Teheran im Einsatz, um Demonstrationen zu unterbinden. Die „Grüne“ Revolution hat dadurch an Momentum verloren. Das Gelände der Universität wurde von der Polizei abgeriegelt. Einheiten von Polizei und Basidsch-Milizen besetzten alle größeren Plätze. 

Der Wächterrat entschied unterdessen, zehn Prozent der Wahlurnen nachzählen zu lassen. Mir Hossein Mussawi, einer der unterlegenen Kandidaten hat inzwischen einen Brief an den Wächterrat veröffentlicht, in dem er den Vorwurf erhob, das Ergebnis der Wahl, die den Amtsinhaber Mahmud Ahmadinedschad bestätigt, sei schon Monate im voraus geplant gewesen. Sowohl Moussawi als auch Mehdi Karroubi nahmen nicht an einer Sitzung mit dem Wächterrat teil, bei der es um die 646 Beschwerden über Unregelmäßigkeiten bei der Wahl ging.

Den bei der Wahl unterlegenen Kandidaten wurden inzwischen angedroht, man werde sie zur Verantwortung ziehen, wenn ihre Anhänger weiter demonstrieren. Moussawi erklärte dabei, er werde im Rahmen seines Kampfes um das Wahlergebnis zum Märtyrer zu werden, falls nötig. Auch in der Nacht vom Freitag zum Samstag ertönten wieder Rufe „Tod dem Diktator!“ und „Allahu akbar!“ von den Dächern der Hauptstadt. 

An Demonstrationen von Exiliranern in der ganzen Welt nahmen Tausende teil, auch in Deutschland. Vom amerikanischen Fernsehsender CBS zur Situation befragt, erklarte US-Präsident Barack Obama seine Besorgnis über „Tenor und Tonfall“ der Erklärung Chameneis. Barack verlangte vom Iran, „jegliche Akte der Gewalt und der Ungerechtigkeit gegen das eigene Volk“ zu beenden, die „ganze Welt schaut zu.“ Nach Obama müsse das Recht auf Versammlungs- und Meinungsfreiheit beachtet werden.

Unweit des Imam-Chomeini-Schreins wurde nach Angaben des staatlichen Fernsehens ein Selbstmordanschlag verübt. Dabei wurden der Attentäter und eine weitere Person getötet sowie acht Personen verletzt. Die Stätte gilt vielen Iranern als Heiligtum. Da die Bewegungsfreiheit ausländischen Journalisten beschnitten wurde, konnte dieser Bericht nicht bestätigt werden. Inzwischen verbreitete sich über Twitter die vielfach im Ausland weitergeleitete Nachricht, dass die Explosion am Schrein vom Regime inszeniert worden sei und „nicht das Werk von Terroristen“. Die Weiterleitung von Tweets erschwert die Rückverfolgung. Viele Neuigkeiten werden über Twitter verbreitet und erst später von Nachrichtenagenturen gemeldet. Am Samstag waren unter den Tausenden von Tweets auch Meldungen, dass es zu blutigen Gefechten komme, die Straßen seien „voll von Steinen und Feuer“, anderere Tweets sprechen davon, dass Anwohner Flüchtende in ihren Hausfluren verbergen, oftmals auch Verletzte, die von der Polizei „brutal geschlagen“ würden.