"Iran, if there were any kind of activity of any sort, is not going to be quiet and would react fiercely," he told reporters on the sidelines of the World Petroleum Congress when asked what Tehran would do in the event of an attack.

"When just a statement (about a possible attack) makes this much volatility in the market, can you imagine that if any action happens ... what would be the result in the oil market?" he said through a translator.

When questioned about whether Iran, the world's fourth-biggest oil exporter, would stop exports as a result of an attack, he replied: "Iran has been always a reliable source of supply to the market and Iran remains a supplier forever."

He also stressed during a presentation to delegates here that "oil and gas as other energies are industries of peace and friendship."

There has been a surge in speculation recently that Israel might be planning a military strike against Iran's nuclear sites.

Iran insists its atomic drive is entirely peaceful and it needs nuclear energy for a growing population whose fossil fuels will eventually run out. Western powers fear it is using the programme to develop nuclear weapons.

The United States and its regional ally Israel have never ruled out military strikes to end what they see as Tehran's defiance, and speculation of an attack mounted last month after it emerged Israel had carried out practice runs.

Russia, which has always insisted the crisis should be solved through diplomacy, issued a stark warning about the dangers of a military strike.

"All this is very dangerous. If force is used it will be catastrophic for the whole Middle East," a Russian foreign ministry official told journalists on condition of anonymity.

Nozari also ruled out increasing supply to cool record crude prices.

"We have got some spare capacity for production. At the same time, there is no need for more supply of oil to the market," he said.

Consumer nations have been pressing Iran and fellow members of the Organisation of Petroleum Exporting Countries to increase supply to bring down prices of more than 140 dollars a barrel.

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