EDITOR'S NOTE: Iranian authorities have barred journalists for international news organizations from reporting on the streets and ordered them to stay in their offices. This report is based on the accounts of witnesses reached in Iran and official statements carried on Iranian media. By KARIN LAUB Associated Press Writer EDITOR'S NOTE: Iranian authorities have barred journalists for international news organizations from reporting on the streets and ordered them to stay in their offices. This report is based on the accounts of witnesses reached in Iran and official statements carried on Iranian media. ------ A senior Iranian cleric demanded in a nationally broadcast sermon Friday that leaders of election protests be punished harshly, with some 'worthy of execution.' The country's increasingly isolated opposition leader effectively ended his role in the demonstrations, saying he'll seek permits for future rallies. Iran's ruling clergy has widened its crackdown on the opposition since the bitterly disputed June 12 presidential election, and scattered protests have replaced the initial mass gatherings. 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. Mousavi has said victory was stolen from him through fraud, challenging the proclamation of hard-line President Mahmoud Ahmadinejad as the winner. 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. Hundreds have been detained since the vote, including journalists, academics and university students, and a special court has been set up to put them on trial. At least 17 people have been killed in the protests, in addition to eight members of the pro-government Basij militia, the government has said. President Barack Obama, joined at the White House by German Chancellor Angela Merkel, hailed the demonstrators in Iran and condemned the violence against them. 'Their bravery in the face of brutality is a testament to their enduring pursuit of justice,' Obama said. 'The violence perpetrated against them is outrageous. In spite of the government's efforts to keep the world from bearing witness to that violence, we see it and we condemn it.' Obama scoffed at accusations Thursday of U.S. meddling in Iran by Ahmadinejad, who called for 'repentance' by the U.S. leader. Obama added that Mousavi has 'captured the imagination or spirit' of those inside Iran who are 'interested in opening up.' In a Friday 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 alleged that 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, interrupted by worshippers' chants of 'Death to Israel.' Earlier this week, Iran expelled two British diplomats, 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. Also Friday, more than 150 demonstrators attacked the Iranian Embassy outside the Swedish capital of Stockholm, throwing stones, breaking windows and injuring one worker, police said. Officers evicted the few demonstrators who climbed in through broken windows and arrested one person, said police spokesman Ulf Hoglund. 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 London, an Iranian doctor who said he tried to save Soltan as she bled to death, told the BBC she apparently was shot by a member of the Basij militia. Protesters spotted an armed member of the militia on a motorcycle, and stopped and disarmed him, said Dr. Arash Hejazi. The man appeared to admit shooting Soltan, shouting 'I didn't want to kill her,' but the furious protesters confiscated his identity card and took photographs of him before letting him go, Hejazi said. 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 and placing flowers on her grave, witnesses said. Vigils for Soltan have been held around the world. 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 in advance. The opposition leader noted that Ahmadinejad has been able to hold two postelection 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 trying 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 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. On Wednesday, 70 university professors were detained after meeting with Mousavi. All but four have been released. Those still in custody included his former campaign manager. ---------- Laub reported from Cairo; Associated Press writers Shaya Tayefe Mohajer in Cairo, Louise Nordstrom in Stockholm, and Ben Feller in Washington contributed to this report. 