Shock Twitter pictures of bloody crackdown on Iran election protests

Using the website Twitter to get round a media blackout, students sent this and other shocking pictures to the Evening Standard today with the message: "We just want the world to know the truth."

The man is one of at least 20 unarmed people believed to have been killed and scores wounded in five days of mass demonstrations following claims that president Mahmoud Ahmadinejad rigged Friday's election.

There are reports that soldiers have been given orders to fire on protesters as the regime tries to control the biggest uprising since the Islamic revolution 30 years ago that swept the ayatollahs to power.

In an attempt to suppress images of the unrest, the Iranian government yesterday barred foreign media from leaving their offices to report on demonstrations.

The Revolutionary Guard, an elite military force answering to supreme leader Ayatollah Ali Khamenei, told Iranian websites and bloggers to remove any materials that "create tension".

Iranians were barred from accessing sites through telecommunications networks and firewalls were put up blocking sites, but many have been able to get round the blocks using networking site Twitter which has become a vital method of communication with the outside world.

One user blogging under the name "Girlintehran" wrote: "The revolution guard wants us to stop posting messages. We just want the world to know."

She then sent a message to the Standard linking to an image of a computer screen that had been smashed, pleading with us to "publish what is really going on".

On Monday there were reports that four students had been killed in a raid on a dormitory at Tehran university amid claims that some were "thrown from windows" by secret police.

Many of the protests are being organised by students at universities across Iran.

They are leading the campaign to back defeated candidate Mirhossein Mousavi and want the election result to be annulled. Iranian students in Britain and the US are also playing a key role.

Twitter has become so crucial in providing a communication outlet for Iranians that the US state department yesterday persuaded bosses at the site to delay an upgrade that would have halted daytime service in Iran.

Twitter then moved its maintenance blackout so it would take place in the middle of the night in Iran.

Another user "IranRiggedElect" revealed in a post today: "France ambassador in Iran was summoned by the Iranian gov. after Sarkozy calling the results a fraud."

Some used the site to make claims about the extent of the violence perpetrated by the Revolutionary Guard and their paramilitary group the Basiji.

User "2Hamed", a student in Tehran, wrote: "Dead students bodies who were killed by Gov. were buried secretly."

The user urged supporters to "wear green to show support for Mousavi" or "black to mourn martyrs".

Another Twitter user reported that access to some sites was being blocked.

"Iranelections" wrote: "finally back on Twitter, severe problems in access to most services, including GMail, Yahoo Messenger, Skype, Facebook."

One student, Sara Ahmadi, from the Sharif university in Tehran, sent a message to the Standard with photographs of rooftop protests.

The activist for the Socialist Islamist group the People's Mujahideen of Iran, wrote today: "In most of the cities the revolutionary guards attacked people and shot them with guns.

"The protests are not being decreased, they are being repressed. The revolutionary guards have announced that they have the okay to shoot people, and more than 20 so far have been killed."

Other sites including YouTube were used to post videos of the violence, including demonstrators being treated for gunshot wounds.

Today Mr Mousavi used his Facebook page to communicate with nearly 60,000 supporters, saying: "I ask the people to express their solidarity with the families .... by coming together in mosques or taking part in peaceful demonstrations."

Internet analysts and bloggers were today describing this as "Twitter's finest hour".

While the Iranian government has been able to block access to Facebook and YouTube intermittently, Iranians have managed to post messages and links on Twitter, which allows users to blog in 140-character bursts.

Bloodshed, mass protests, arrests and a media crackdown have focused world attention on Iran, the fifth-biggest oil exporter, which is locked in a nuclear row with the West.

The political earthquake set off by Friday's vote prompted President Obama, who had urged the Iranian leadership to "unclench its fist", to say the upheaval showed that "Iranian people are not convinced with the legitimacy of the election".

Major Western nations have questioned the fairness of the result which gave Mr Ahmadinejad a landslide victory. Discord within Iran's ruling system has never been so public.

The Mousavi camp is backed by traditional establishment figures, such as former presidents Akbar Hashemi Rafsanjani and Mohammad Khatami, concerned about how Mr Ahmadinejad's aggressive foreign policy and populist economics are shaping Iran's future.