Protestors in Iran on Monday used Twitter for battle cries and to spread word about clashes with police and "hard line supporters" of President Mahmoud Ahmadinejad.
Twitter messages, some with links to pictures, streamed from Iran despite reported efforts by authorities there to block news of protests over Ahmadinejad's claim of having been fairly re-elected.
Pictures of wounded or dead people that senders claim were Iranian protestors ricocheted about Twitter and wound up posted at online photo-sharing websites such as Flickr.
A protestor was reportedly shot dead during clashes in Tehran on Monday as massive crowds of people defied a ban to stage a rally against the disputed re-election of Ahmadinejad.
A local photographer said the protestor had been shot with a bullet to the head and that more were wounded when violence erupted outside a local base of the Islamic Basji militia, which had been set ablaze.
People were seen fleeing the area as police fired tear gas on protestors who set motorbikes, tires and dustbins ablaze, a news agency AFP correspondent said, as huge clouds of black smoke billowed into the sky.
The violence flared after Ahmadinejad's defeated rival Mir Hossein Mousavi appeared in public for the first time since an election that has sharply divided the nation and triggered protests and rioting.
"Iranelection" was the top Twitter trend of the day, and a message thread led by "Persiankiwi" appeared to be orchestrating hacker attacks on official Iran websites while firing off updates on developments in the streets.
"We are going offline to get a phone free for calling out," Persiankiwi tweeted at mid-day. "We are also moving location - too long here - is dangerous."
A subsequent Persiankiwi tweet reads "Attacked in streets by mob on motorbikes with batons - firing guns into air - street fires all over town -- roads closed."
Twitter users were also slamming mainstream media outlets for not covering the Iranian election aftermath more intensely.
A "CNNfail" threat at the U.S.-based micro-blogging service critiqued the cable news network's coverage throughout the weekend.
"This is all seriously power to the people, in more ways than one," a Twitter member using the screen name "kianarama" tweeted in exchanges at CNNfail and Iranelection on Monday.