Iran has no interest in nuclear weapons, but will keep pursuing peaceful nuclear energy, its Supreme Leader Ayatollah Ali Khamenei told heads of state from developing countries in Tehran.

Iran, hosting a summit of the 120-nation Non-Aligned Movement, is hoping the high-profile event will prove Western efforts to isolate and punish it economically over a disputed nuclear programme have failed.

"Our motto is nuclear energy for all and nuclear weapons for none," Mr Khamenei said.

United Nations Secretary General Ban Ki-moon, attending the summit, had urged Mr Khamenei to take steps to prove Iran's nuclear work is peaceful.

The West suspects Iran is seeking a nuclear weapons capability, an accusation Tehran denies.

Mr Khamenei criticised the UN Security Council as an illogical, unjust and a defunct relic of the past used by the United States "to impose its bullying manner on the world".

He added: "They [Americans] talk of democracy when what they have is military intervention in other countries."

The US and Israel had frowned on the decision by Mr Ban to attend the summit but the UN chief, without naming Iran, hit out at countries which denied the Holocaust.