The Guards: Army, political player and business empire

The Iran Revolutionary Guards Corps (IRGC) was set up after the 1979 Islamic revolution to protect the ruling system against internal and external threats and to uphold revolutionary values. The IRGC answers to Supreme Leader Ayatollah Ali Khamenei, the Islamic Republic's top authority.

It controls the Basij religious volunteer militia, which carried out "human wave" attacks in the 1980-88 war with Iraq. The Basij are Iran's moral police, enforcing Islamic social codes and quelling civil unrest. They are said to number millions.

Qods Force is a shadowy IRGC special operations unit, handling activities abroad. The United States, which says the Qods Force backs militants in Iraq, Lebanon and Afghanistan, has imposed sanctions on firms and individuals linked to what it brands a terrorist organisation. The United States has also designated the IRGC a proliferator of weapons of mass destruction for what it says is its role in Iran's nuclear and ballistic missile programmes.

What are its military capabilities?

The IRGC initially focused on internal security but became a more organised combat force during the war with Iraq. It now has about 125,000 fighters with army, navy and air units. It operates separately from the 350,000-strong regular army. Guardsmen fought in conventional battles against Iraq. The IRGC controls Iran's strategic missile forces and has played a key role in developing advanced systems such as the Shahab-3 missile with a range of 2,000km.

How does it operate in the political system?

The IRGC's mandate to protect revolutionary values has prompted it to speak out when it felt the system was threatened.

General Yadollah Javani, director of the IRGC's political arm, said the Guardsmen, who suppressed post-election protests this year, had thwarted an attempt to overthrow Islamic rule.

The IRGC's influence appears to have grown since hardline President Mahmoud Ahmadinejad came to power in 2005. Two-thirds of his first 21-man cabinet were IRGC veterans, like himself.

Some analysts suggest the corps' political power already eclipses that of Ahmadinejad. Given Khamenei's reliance on the Guard to quell dissent, the supreme leader himself may now be hostage to the force he commands, some analysts argue.

Others say the IRGC leadership is factionalised and lacks the cohesion to exercise power independently. Some ex-Guard officers, such as Parliament Speaker Ali Larijani, Tehran mayor Mohammad Baqer Qalibaf and defeated presidential candidate Mohsen Rezai, are critics of Ahmadinejad.

The IRGC also conducts popular military training, operates a domestic media apparatus and runs education programmes to inculcate loyalty to the revolution.

What about business interests?

After the war with Iraq, the IRGC became heavily involved in reconstruction and has expanded its work to cover areas such as import-export, oil and gas, defence, transport and construction.

It has become a major contractor, with ties to firms controlling billions of dollars in business, construction, finance and commerce, the US Treasury has said.

A Rand Corporation report this year said Khatam Al Anbia, an engineering firm affiliated to the IRGC, had been awarded more than 750 contracts in construction, infrastructure and energy projects.