Protests in Iran continued Thursday as demonstrators wore black to mourn those killed in clashes throughout the week.
An Iranian-American researcher in Tehran, who is a supporter of presidential challenger Mir Hossein Mousavi, says the mood at the protest was calm. But, he says, the calm of the day gives way to a more unsettling night.
Out of concern for his safety, he prefers that his name and other details about him are not used.
"I've described to friends back home that Tehran has become two cities," he says. "I think from about 4 in the afternoon to about dinnertime, it is this site where both (Iranian President) Ahmadinejad and Mousavi's supporters show up and demonstrate peacefully.
"However, at night, what we're hearing and seeing, are Basij, or the state paramilitary forces ... confronting either people who are provoking them or themselves taking things into their own hands."