The main force, named the Special Unit of Martyr Seekers in the Revolutionary Guards, was first seen last month when members marched in a military parade, dressed in olive-green uniforms with explosive packs around their waists and detonators held high.

Dr Hassan Abbasi, head of the Centre for Doctrinal Strategic Studies in the Revolutionary Guards, said in a speech that 29 western targets had been identified: “We are ready to attack American and British sensitive points if they attack Iran’s nuclear facilities.” He added that some of them were “quite close” to the Iranian border in Iraq.

In a tape recording heard by The Sunday Times, Abbasi warned the would-be martyrs to “pay close attention to wily England” and vowed that “Britain’s demise is on our agenda”.

At a recruiting station in Tehran recently, volunteers for the force had to show their birth certificates, give proof of their address and tick a box stating whether they would prefer to attack American targets in Iraq or Israeli targets.

President Mahmoud Ahmadinejad warned last Friday that Israel was heading towards “annihilation”. He was speaking at a Tehran conference on Palestinian rights aimed at promoting Iran as a new Middle Eastern superpower.

According to western intelligence documents leaked to The Sunday Times, the Revolutionary Guards are in charge of a secret nuclear weapons programme designed to evade the scrutiny of the International Atomic Energy Agency.

One of the leaked reports, dating from February this year, confirms that President George W Bush is preparing to strike Iran. “If the problem is not resolved in some way, he intends to act before leaving office because it would be ‘unfair’ to leave the task of destroying Iran’s nuclear facilities to a new president,” the document says.

Alireza Jafarzadeh, a former spokesman for National Council of Resistance of Iran (NCRI), an opposition group, said a secret, parallel military programme was under way. According to sources inside Iran, the Revolutionary Guards were constructing underground sites that could be activated if Iran’s known nuclear facilities were destroyed.

The NCRI is the political wing of the Mujaheddin-e-Khalq, which is deemed a terrorist organisation in Britain and America. However, much of its information is considered to be “absolutely credible” by western intelligence sources after Jafarzadeh revealed the existence of the Natanz plant in 2002.

Within the past year, 14 large and several smaller projects have been created, according to Jafarzadeh. Several are designed to be nuclear factories; others are for the storage of weapons, he claimed.

Additional reporting: Safa Haeri

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