Over two weeks of protests mark the most serious challenge in years to Iran's theocratic leadership in their scale and nature but it is too early to predict the immediate demise of the Islamic republic, analysts say.

The demonstrations moved from protesting economic grievances to demanding a wholesale change from the clerical system that has ruled Iran since the 1979 revolution that ousted the shah.

The authorities have unleashed a crackdown that, according to rights groups, has left hundreds dead while the rule of supreme leader Ayatollah Ali Khamenei, now 86, remains intact.

"These protests arguably represent the most serious challenge to the Islamic republic in years, both in scale and in their increasingly explicit political demands," Nicole Grajewski, professor at the Sciences Po Centre for International Studies in Paris told AFP.

She said it was unclear if the protests would unseat the leadership, pointing to "the sheer depth and resilience of Iran's repressive apparatus".

The Iranian authorities have called their own counter rallies, with thousands attending on Monday.

Thomas Juneau, professor at the University of Ottawa, said: "At this point, I still don't assess that the fall of the regime is imminent. That said, I am less confident in this assessment than in the past."

These are the key factors seen by analysts as determining whether the Islamic republic's leadership will hold on to........

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