Iranian officials and clerics are insisting Egypt's insurrection, and similar popular revolts across the Arab world, are inspired by Islamist political ideology and have their origin in the 1979 Iranian revolution that overthrew the late Shah. But opposition leaders and independent analysts take a very different view. They say the common rallying cause is democracy, not Islamism – and that the Tehran regime is increasingly fearful of an Egypt-style uprising there.

After days of nervous hesitation, the Islamic Republic appeared today to have decided what line to take. A statement signed by 214 MPs pledged strong "spiritual" support for Egyptians in opposing "the tyranny of their rulers". It also condemned "efforts by certain western countries [code for Britain and the US] as well as the Zionist regime [Israel] to exhaust the uprising and separate it from Islamic values".

Iran's Supreme Leader, Ayatollah Ali Khamenei, who ordered a violent crackdown on Iran's pro-democracy protesters in 2009, claimed on his webpage to have predicted and personally encouraged Egypt's pro-democracy revolt. He offered no explanation for this apparent contradiction. President Hosni Mubarak's persecution of the Muslim Brotherhood, Egypt's biggest Islamist party, and his collusion with the US and Israel, were his undoing, Khamenei suggested.

In a webpage entry entitled Supreme Leader's View Of Egypt, quoted by Shayan Ghajar on InsideIran.org, Khamenei said the Brotherhood's struggle "is just like the yell that the Iranian nation let out against America and against global arrogance and tyranny" in 1979.

Other Iranian officials are singing the same tune. Major-General Yahya Rahim Safavi, Khamenei's military adviser, told Fars news agency that Mubarak would share the same fate as the shah, vanquished by the forces of Islamist revolution. And in case western governments missed the point, pro-regime cleric Ayatollah Seyyed Ahmad Khatami rammed it home. The uprisings heralded "an Islamic Middle East" based on religion and religious democracy, he said. Iranian-style Islamist governance, not US-style liberal democracy, was the coming model.

This official Iranian interpretation of events is open to challenge, to put it mildly. Evidence so far from the streets of Cairo and Tunis suggests Islamist groups have followed, rather than led the popular mood. Egypt's protesters say they are united in opposition to Mubarak, as a symbol of injustice, and are protesting against a lack of democratic freedoms, poverty, a dearth of economic opportunity, and official corruption. Islam is not much mentioned.

Purists point out the Iranian revolution was not, initially, Islamist-led. It, too, was intrinsically a response to poor governance. This is why, paradoxically, Mir Hossein Mousavi, the Iranian opposition leader who many believe defeated Mahmoud Ahmadinejad in the 2009 presidential election, is also lauding events in Egypt – and claiming credit.

"What we are witnessing in the streets of Tunis, Sana'a, Cairo, Alexandria and Suez take their origins from the millions-strong protests in Tehran in 2009," Mousavi said on his Persian-language website, Kalemeh.com.

Shayan Ghajar said Iran's attempts to spin the story revealed "more about the Islamic Republic's anxiety than the actual facts on the ground in Cairo".

Western governments will have differing assessments of the Islamist role in events in Egypt. But Iran's mullahs have at least one firm if unlikely ally in their corner: Israel. Step forward Israeli prime minister Binyamin Netanyahu. "Our real fear," Netanyahu said this week, was that Egypt and other destabilised Arab governments could become "repressive regimes of radical Islam".