Anti-government protests by thousands of Iranians inspired by the revolutions in Egypt and Tunisia show Iran's "Green" pro-democracy movement is still alive despite a fierce crackdown by the authorities.
But the chances of demonstrations snowballing into the kind of uprising that swept veteran Egyptian and Tunisian rulers from power seem remote in the near term, since Iran's security forces are united in defending the 32-year-old Islamic Republic.
Monday's rallies in Tehran and other cities, in which two people died and dozens were wounded and arrested, were the first big show of opposition on the streets since authorities crushed protests against a disputed 2009 presidential election.
"After 20 months of oppression and more than a year without a significant public rally, despite the house arrests of its key figures, and in the face of intimidation and beatings, the Green Wave proved that it could still surge," analyst Scott Lucas of Birmingham University wrote on the EA Worldview website.
The scale of the protests seemed to take the authorities by surprise and contrasted starkly with government assertions that the Green movement is a spent force, and that support for the Islamic system is overwhelming.
"The regime for two years claimed that it had finished what it called the biggest conspiracy, or as we call it the Green movement. They arrested, they executed, they killed, they tortured, raped ... to prevent any more demonstrations," said Alireza Nourizadeh, director at the Centre for Arab and Iranian Studies in London.
"Yesterday it showed that they are wrong and the people still have hope," he said.
State television branded the protesters "hypocrites, monarchists, thugs and seditionists", and Parliament President Ali Larijani accused the United States of supporting them to distract attention from its own setbacks in the Middle East.
Hardline Iranian lawmakers urged the judiciary to hand down death penalties to reformist opposition leaders Mehdi Karroubi and Mirhossein Mousavi, the two defeated presidential candidates, for fomenting the unrest, state media reported.
Denied a permit for a rally in solidarity with the Egyptian and Tunisian movements, the two are under house arrest. Security forces prevented them attending the march, arrested at least 20 pro-reform activists before the rally and took their websites offline, opposition activists reported.
But witnesses said the mostly middle-class protesters who defied the ban and converged on Tehran's Azadi (Freedom) Square barely mentioned the names of Mousavi and Karroubi.
Their slogans were aimed directly against Supreme Leader Ayatollah Ali Khamenei, branded a "tyrant", rather than at hardline President Mahmoud Ahmadijenad, the witnesses said.
That suggests support for reformists trying to improve the Islamic system from within may have been overtaken by a more radical opposition to the entire system.
"Because the regime expends all its efforts on saying that everything's normal and everyone loves us, even small signs of dissent are significant in puncturing this fiction," said Ali Ansari, professor of Iranian studies at St. Andrews University.
"This will give people in Iran hope."
While the authorities' verbal tirades against the protesters have been fierce, the demonstrators were treated less violently than those who took to the streets in 2009 to denounce alleged vote-rigging in favour of Ahmadinejad. The elite Revolutionary Guards and the Basij militia were mostly kept off the streets and out of sight on Monday. Instead, uniformed police and plainclothes agents were deployed to control the crowds and they used mostly non-lethal teargas rather than live ammunition, to avoid causing casualties.
Nevertheless, one person was shot dead and another killed in unexplained circumstances. A conservative lawmaker, Kazem Jalali, described them as "martyrs", implying they had been killed by "terrorists" rather than security agents. Police prevented protesters from staying on overnight in the square, a rallying point for the 1979 Islamic revolution that overthrew the Shah, in an attempt to turn it into a permanent focal point as Egyptian activists did in central Cairo.
"This is not Tunisia. This is not Egypt. This is Iran, where Azadi Square did not become the new Tahrir Square yesterday," Lucas said.
WRITING ON WALL?
While the political support base for the Iranian system has narrowed in recent years due to the exclusion of reformists and dissident clerics, and to endemic factional feuds, the security forces show every outward sign of remaining loyal to the regime.
Unlike in Tunisia and Egypt, where the army command's refusal to open fire on the people led to the fall of entrenched dictators, Iran's security and intelligence forces showed in 2009 they were willing to use lethal force repeatedly.
Revolutionary Guard veterans hold key government positions from Ahmadinejad on down, and control major business interests. The Basij militia is under strong ideological control. The regular army is weak and kept well away from internal security.
"Iran is not going to be the sort of country like Egypt where it's all going to unravel in a few weeks," Ansari said. "But for me the writing is on the wall. This has shown the leadership that they cannot terrorise people into submission."