One person captured on Internet videos helping "Neda", the young Iranian woman killed last week who has become an icon of the protests, was identified by a British newspaper on Friday as a doctor who has since fled Iran.
"I felt she was trying to ask a question, why?' Dr Arash Hejazi told the Times in an interview as he recalled her final moments lying in a street with blood pouring from her body.
"She was just a person in the street who was against the injustice going on in her country, and for that she was murdered," said Hejazi, an Iranian who is resident in Britain but says he went to Tehran on a business trip.
Hejazi said a government militiaman killed Neda Agha Soltan, a 26-year-old music student.
Iran has accused the West, particularly Britain and the United States, of inciting violence. State television has blamed violence on "terrorists" and "vandals".
Hejazi, 38, said he fled from Iran when the video footage sped around the world on websites because he feared his own life might be in danger as he could be seen with Soltan.
Before trying to leave, he said he emailed a friend in Britain to say he hoped to join his family in the university city of Oxford where he was studying: "If something happens to me, please take care of (my wife and son)."
He said he had gone outside into Tehran's streets only when he and some friends heard a commotion.
Hejazi said Soltan's death would always haunt him but was glad she had become a global
"This way her blood is not wasted and she did not die in vain," he said.
In Iran, supporters of defeated candidate Mirhossein Mousavi, who says the June 12 presidential poll was rigged, plan to release thousands of balloons on Friday with the message: "Neda you will always remain in our hearts."
About 20 people were killed when the disputed poll sparked the worst unrest in Iran since the Islamic revolution in 1979.
A security crackdown by Iran's hardline government has largely driven demonstrators off Tehran's streets this week.