TEHRAN - Iranian supreme leader Ayatollah Ali Khamenei warned Western leaders on Monday of a "firm fist" in response to their "meddling" in Iran's domestic affairs.

"The leaders of arrogant countries, the nosy meddlers in the affairs of the Islamic republic, must know that no matter if the Iranian people have their own differences, when you enemies get involved, the people... will become a firm fist against you," he said in a televised speech in Tehran.

"The Iranian nation warns the leaders of those countries trying to take advantage of the situation, beware! The Iranian nation will react."

Iranian leaders have accused the West, particularly Britain and the United States, of seeking to destabilise the country in the aftermath of its disputed presidential election.

"We will assess the meddlesome remarks and behaviour of these governments... which will definitely have a negative impact on the Islamic republic's relations with them in the future," state television also quoted Khamenei as saying.

Khamenei made his remarks as Britain confirmed that Iran had released an eighth local British embassy staff member in Tehran, leaving one still in detention.

Iran accused the embassy employees of instigating riots in the unrest that erupted over the June re-election of President Mahmoud Ahmadinejad, which his rivals said was fraudulent and marred by widespread irregularities.

A powerful Iranian cleric had said on Friday that some of the British staff would be put on trial, but did not say how many.

Khamenei has described Britain, which has long had turbulent relations with Iran and a long history of mistrust, as the "most evil" of its enemies.