"The Iranian nation is not seeking a nuclear weapon," Khamenei said in a speech broadcast live on state television to mark the anniversary of the death in 1989 of revolutionary leader Ayatollah Ruhollah Khomeini.

"We are seeking nuclear energy for peaceful purposes for daily use and we will continue this path to the envy of our enemies. We will mightily achieve this aim."

Khamenei has in the past frequently stated Iran's nuclear programme is peaceful and that nuclear weapons are against Islam. But the vehemence and detailed explanation in Tuesday's speech was unusual.

His comments come a day after UN atomic watchdog chief Mohamed ElBaradei urged "full disclosure" over allegations that Tehran hid key information about weaponisation in its contested nuclear programme.

The International Atomic Energy Agency (IAEA) has in the past few months been investigating intelligence given by Western countries that Iran has studied how to make an atomic weapon, much to Tehran's fury.

In its report, the IAEA expressed "serious concern" that Iran was hiding information about alleged studies into making nuclear warheads as well as defying UN demands to suspend uranium enrichment.

The watchdog is currently holding its summer meeting of the 35-member board of governors, and the Iranian nuclear programme is a key issue.

But Khamenei said: "You know the Iranian nation is in principle and on religious grounds against the nuclear weapon. Nuclear weapons only incur high costs and have no use. They do not bring power to a nation."

Khamenei also expressed concern that "terrorists" could one day gain possession of a nuclear bomb and cause havoc throughout the world.

"Sooner or later, international terrorists will get their hands on nuclear weapons and take away from security from the world arrogance and all the nations," he said.

The United States and its European allies fear Iran wants to use the sensitive process of uranium enrichment to make an atomic weapon. The UN Security Council has imposed three sets of sanctions against Tehran over its refusal to suspend enrichment.

But Tehran, OPEC's number two oil producer, insists its drive is entirely peaceful and solely aimed at generating electricity for a growing population whose exploitable hydrocarbon reserves will eventually run out.

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