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.
TEHRAN, Iran — Iran's embattled opposition leader declared Thursday that he won't back down from challenging what he called a rigged presidential election despite the regime's increasing attempts to isolate him, telling the hard-liners: "I won't leave the picture."
Incumbent President Mahmoud Ahmadinejad, proclaimed the landslide winner of the balloting, accused President Barack Obama of meddling in Iran's affairs. "Correct yourself," he told the U.S. leader, urging him to "show your repentance."
On his Web site, opposition leader Mir Hossein Mousavi leveled unusually strong criticism at the Islamic regime's leaders, saying they were "the main factor for the recent violence and unrest and have spilled the blood of the people." His allegation came nearly a week after supreme leader Ayatollah Ali Khamenei warned the opposition to end street protests or be held responsible for any "bloodshed and chaos."
Khamenei has refused to order a new vote despite the biggest demonstrations in the country since the 1979 Islamic Revolution.
"I am not ready to withdraw from demanding the rights of the Iranian people," Mousavi said, adding that he was determined to prove electoral fraud.
"They are not aware that I won't leave the picture with these accusations," he said.
Authorities arrested 70 university professors Wednesday after they met with Mousavi, and all but four were later released, his Web site said. Those still in custody included Qorban Behzadiannejad, Mousavi's former campaign manager.
Mousavi's political adviser, Mohammad Reza Tajik, denied reports that Mousavi was under house arrest.
State media reported that in addition to the 17 protesters killed in the unrest, eight members of the pro-government Basij militia were killed and dozens more wounded by weapons and knives. The reports could not be independently verified.
Khamenei has unleashed the Basij and the feared Revolutionary Guard, authorizing them to use whatever force is deemed necessary to squelch dissent. He has also ordered a large security detail around Mousavi — ostensibly to protect him, but presumably also to restrict his movements.
There were no reports of rallies Thursday. Another opposition figure, presidential candidate Mahdi Karroubi, had planned a march but it was postponed for lack of a permit, a day after club-wielding security forces dispersed a small group of protesters outside Iran's parliament.
Honoring the 'martyrs'
Mousavi's Web site, Kalemeh, said he applied for permission to hold a gathering to commemorate the "martyrs" of the postelection campaign. The statement did not elaborate or give a date.
Obama and other Western leaders have become increasingly outspoken over Tehran's brutal crackdown on protesters. Since Saturday, demonstrators challenging the election results have found themselves increasingly struggling under a blanket crackdown by government authorities.
Iran has already tangled with Britain, expelling two British diplomats after accusing that country of stirring up unrest and sending spies to Iran, and state TV quoted Ahmadinejad as comparing Obama to former President George W. Bush.
"We expect nothing from the British government and other Europeans governments, whose records and backgrounds are known to everybody and who have no dignity," Ahmadinejad said. "But I wonder why Mr. Obama, who has come with the slogan of change, has fallen into this trap, the same route that Mr. Bush took and experienced its ending."
Before the election, the Obama administration had indicated it was interested in reaching out to Iran after years of a diplomatic freeze following the revolution. Iran has given no clear signal it is interested in the U.S. overture, and in the wake of the vote, Obama said Washington and the world were "appalled" by the crackdown.
Ahmadinejad, who is to be sworn in for a second four-year term by August, warned there would be "nothing left to talk about" if Obama kept up such a tone. "This will not have any result, except that the people will consider you similar to Bush," he said.
Asked about Ahmadinejad's statement, White House spokesman Robert Gibbs said the Iranian president is among those who are trying to blame the United States for the unrest. "I would add President Ahmadinejad to that list of people trying to make this about the United States," he said.
Despite being soundly backed by Khamenei, whose word is law in Iran, Ahmadinejad appeared to have lost some face both at home and among traditional allies.
Parliament speaker Ali Larijani was among 185 of 290 lawmakers who stayed away from a victory celebration for Ahmadinejad earlier this week, several Tehran newspapers reported.
Iran's most senior dissident cleric, Ayatollah Hossein Ali Montazeri, warned the authorities that trying to snuff out dissent would prove futile.
If people are not allowed to voice their demands in peaceful gatherings, it "could destroy the foundation of any government" no matter how powerful, he wrote.
Doctor recounts Neda death
In London, Dr. Arash Hejazi, who said he tried to save Neda Agha Soltan as the young woman bled to death on the streets of Tehran , told the BBC she apparently was shot by a member of the Basij militia.
Hejazi, who is studying in England, said he was visiting friends in Iran when he went to see the protest and heard a gunshot.
"Neda was standing one meter away from me. I turned back and I saw blood gushing out of Neda's chest," he said. "We ran to her and lay her on the ground. I saw the bullet wound just below the neck."
Hejazi said he couldn't stop the bleeding. A video of her death has circulated around the world and made her a symbol of the opposition.
Protesters spotted an armed member of the Basij militia on a motorcycle, and stopped and disarmed him, the doctor said.
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.
NBC News, Reuters and The Associated Press contributed to this report.