TEHERAN: A top Iranian cleric warned the opposition on Friday against holding an anti-government demonstration to counter an official commemoration of the storming of the US embassy by students 30 years ago.

November 4 "is a day of struggle against oppression worldwide," Ahmad Jannati, head of the powerful Guardians Council, said in a Friday prayer sermon broadcast on state radio.

"Some people who have made plans for this day must know that their plans will fail," he said.

On November 4, 1979, Islamist students stormed the US embassy in Tehran and took American diplomats hostage, holding them for 444 days in a crisis that provoked the severance of diplomatic relations with Washington.

Since then the authorities have organised an annual demonstration to commemorate the event, but this year calls have gone out on the Internet for the opposition to stage a counter-demonstration.

On September 18, opposition supporters took to the streets in their tens of thousands during another annual protest, the pro-Palestinian Quds (Jerusalem) Day, to voice support for main opposition leader Mir Hossein Mousavi.

Mousavi came second to Mahmoud Ahmadinejad in the June 12 presidential election that returned the hardliner to power.

Jannati said in his Friday sermon also accused opposition supporters of having links to the United States and to the Jewish state, saying they wanted "to show their American-Israeli nature" on November 4.

"If they could, they would chant 'Long live America, long live Israel'... but any action that goes against the path of the people and against Velayat (religious rule) is destined to fail," he said.

"May God slice off the hands of those who wish to play with the blood of our martyrs and fighters."

He accused opposition supporters of "seeking to overthrow the regime," and demanded that the authorities act firmly against them.

"If the judiciary and the intelligence services act lightly, this would be a betrayal," Jannati said. "You cannot treat with kid gloves those who have acted like our worst enemies."

Dozens of people were killed and some 4,000 opposition backers were arrested in a crackdown on street violence that erupted after Ahmadinejad's disputed re-election, which the opposition has said was the result of fraud.

The post-election unrest plunged the regime into its worst internal crisis since the founding of the Islamic republic in 1979 by Ayatollah Ruhollah Khomeini.