Iran's increasingly isolated opposition leader effectively ended his role in street protests, saying he'll seek permits for future rallies. A leading cleric demanded in a nationally broadcast sermon Friday that leaders of the unrest be punished harshly and that some are "worthy of execution."

Iran's ruling clergy has widened its clampdown on the opposition since a bitterly disputed June 12 presidential election, and scattered protests have replaced the initial mass rallies.

The official Web site of opposition leader Mir Hossein Mousavi, his main tool of communicating with his supporters, was hacked Friday, leaving it blank, an aide said.

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Mousavi has said victory was stolen from him through fraud, challenging the proclamation of President Mahmoud Ahmadinejad as the winner.

However, Mousavi has sent mixed signals to his supporters in recent days, asking them not to break the law, while pledging not to drop his challenge of the election results.

Hundreds have been detained in recent weeks, including journalists, academics and university students, and a special court has been set up to try them.

In Friday's central Muslim sermon at Tehran University, a senior cleric, Ayatollah Ahmed Khatami, called for harsh retribution for dissent.

"Anybody who fights against the Islamic system or the leader of Islamic society, fight him until complete destruction," he said in the nationally broadcast speech.

The cleric claimed some involved in the unrest had used firearms.

"Anyone who takes up arms to fight with the people, they are worthy of execution," he said. "We ask that the judiciary confront the leaders of the protests, leaders of the violations, and those who are supported by the United States and Israel strongly, and without mercy to provide a lesson for all."

Khatami said those who disturbed the peace and destroyed public property were "at war with God," and said they should be "dealt with without mercy."

He reminded worshippers that Iran's supreme leader, Ayatollah Ali Khamenei, rules by God's design and must not be defied.

The cleric also lashed out at foreign journalists, accusing them of false reporting, and singled out Britain for new criticism.

"In this unrest, Britons have behaved very mischievously and it is fair to add the slogan of down with England to slogan of down with USA," he said, as his remarks were interrupted by worshippers' chants of "Death to Israel."

Iran's rulers have accused the West, which has become increasingly vocal in its condemnation of the post-election clampdown, of meddling in Iran's internal affairs. Earlier this week, Iran expelled two British diplomat, prompting the expulsion of two Iranian diplomats by Britain.

In Trieste, Italy, foreign ministers of the Group of Eight countries called for an end to the violence in Iran and urged the authorities to find a peaceful solution.

Khatami, meanwhile, alleged that the icon of the opposition, slain protester Neda Agha Soltan, was killed by demonstrators, not the Iranian security forces. Soltan, 27, was killed by a shot to the chest last week, on the sidelines of a protest.

"The proof and evidence shows that they (protesters) have done it themselves and have raised propaganda against the system," he said. "I say hereby that these deceitful media have to know that the ordeal will be over and shame will remain for them."

In quelling protests, Basij militiamen have broken up even small groups of people walking together to prevent any possible gathering. Still, dozens of friends and relatives of Soltan managed to pay tribute Friday, arriving at Tehran's Behesht-e Zahra cemetery in groups of two and three, uttering brief prayers, placing flowers on Soltan's grave and then leaving, witnesses said.

Vigils for Soltan have been held around the world.

On Friday, Mousavi, who has said he is being increasingly isolated, lost his main link to the world after his official Web site Kalemeh, came up blank and stripped of any text or pictures. Mousavi's associate Ali Reza Beheshti told The Associated Press the site had been taken down by unknown hackers.

In a message on the site late Thursday, Mousavi had said he would seek permission for future protests, even though he said unfair restrictions were being imposed. He said he has been asked by the Interior Ministry to apply in person, a week ahead of time.

The opposition leader noted that his rival, Ahmadinejad, has been able to hold two post-election marches and a Tehran rally "that were well publicized on state television, seeming to encourage participation with their regularly advertised march routes."

Mousavi has said the authorities are pressuring him to withdraw his challenge by attempting to isolate and discredit him. He hasn't led a rally in more than a week.

Khamenei has ordered a large security detail around Mousavi — ostensibly to protect him, but presumably also to restrict his movements. Authorities have also targeted those close to Mousavi.

Late Thursday, state TV reported that the head of Mousavi's information committee, Abolfazl Fateh, was banned from leaving Iran for Britain. The report, which could not be verified independently, identified Fateh as a doctoral student in Britain.

The semiofficial Fars news agency said Fateh was banned from travel so authorities could investigate "some of the recent gatherings," a reference to election protests.

At least 11 Mousavi campaign workers and 25 staffers on his newspaper have been detained since the election.

On Wednesday, 70 university professors were detained immediately after meeting with the opposition leader. All but four have been released. Those still in custody included Qorban Behzadiannejad, Mousavi's former campaign manager.

In all, at least 17 people have been killed in postelection protests, in addition to eight members of the Basij, the government has said.