Egypt's web activists have been brazen critics of the President Hosni Mubarak 30-year rule online. This week's unprecedented protests across Egypt showed they are becoming formidable opponents offline too.

Activists have used Facebook, Twitter and other social media to rally supporters online, coordinate protests and share tips on how to dodge arrest and deal with teargas. They blame the government for making access to the sites patchy.

Mubarak took over Twitter and we took over the streets. Good deal, one anonymous user tweeted.

With two thirds of Egypt's 79 million people under the age of 30 and with many frustrated by largely toothless opposition parties, many of Egypt's youth have turned to the digital sphere as one of the few channels available to express their anger.

The system has not responded to repeated calls for reform, said political analyst Nabil Abdel Fattah. But these new generations managed though virtual space to break that silence and move to the streets.

Analysts say web activists have to prove they can sustain the momentum of protests and may find numbers shrink if the state responds with past tactics such as wage hikes and handouts for the poor instead of the political change they are demanding.

But for now, the web activists, who called for Tuesday's Day of Wrath that kicked off protests now in their third day, are reveling in their success in bringing demonstrators out.

This revolution will be called the revolution of the internet youth, a member of a Facebook group calling for protests wrote. We will take it all the way to the end.

Protesters in Egypt have been inspired by fellow Arabs in Tunisia who toppled their president, Zine al-Abidine Ben Ali, of 23 years. They too spread the word for protests online.

Egyptians have the same complaints that drove Tunisians on to the streets: surging food prices, poverty, unemployment and authoritarian rule that smothers public protests.

DRIVING FORCES

One of the driving forces for Egypt's calls for change was a Facebook group set up by activists enraged by the death of anti-corruption activist Khaled Said, who right groups say was tortured to death in June. Two policemen now face trial.

The activists are not the traditional government critics, showing no religious or other loyalty except to their call for political change.

The Muslim Brotherhood, with it large grassroots network, has stayed largely on the sidelines of the demonstrations. Egypt's registered opposition parties are fractured and weak.

This was a new mixture of young people mobilized primarily using internet technology, said Amr Hamzawy, an analyst at the Carnegie Endowment's Middle East Center.

But without an organized structure beyond the web, online activists may struggle to keep the momentum going.

Hamzawy said that if protests did start faltering, the government may see an opportunity to give concessions on social and economic demands, try to ease tensions a bit, control prices, but ignore the political core of the demands.

In 2008, protests in the industrial city of Mahallah el-Kubra over price rises and shortages of subsidized bread were championed on the web. But the government response, first with tough security and then promises of wage hikes, defused it.

To help protesters stay the course this time, websites have offered a manual for would-be demonstrators on what to do when teargas is fired, how to dodge arrest and tips on a citizen's constitutional rights in case of detention.

'BETTER ORGANISED'

Those have been listed with detailed demands, including a call for Mubarak to quit and the formation of a national unity government, as well as guidance on what to chant. Mobile numbers of supportive lawyers and activists are also listed.

The web allows protest locations to be quickly communicated.

They are becoming better organized, they are able to coordinate, at least to a degree which sustained their activities, Hamzawy said.

Buoyant activists on Facebook are now calling for the biggest protest on Friday, the Egyptian weekend. It gained 75,000 online supporters in about 24 hours.

But the groups are heavily dependent on the internet for networking and coordination, a problem that can slow mobilization if social media networks go down.

Egyptians have already complained of patchy access to Twitter and Facebook, blaming the government, although they have found ways to access the sites via proxies.

Mobile networks and text messages also provide a back up, although users also complain of some disruption.

The government denies any role in disrupting the internet and insists it allows free expression in peaceful protests.

Trying to cut off social media debate is like trying to cut the head off a hydra. Another one grows back very quickly, said Mark Hanson, London-based new media strategist.

According to some web activists, cyber attackers have targeted the Interior Ministry, Communications Ministry and ruling National Democratic Party websites.

The Tunisian model suggests that any government crackdown will struggle to contain the flow of information, and may simply mobilize more web users and other sympathizers into action.

We will not be afraid any longer, many bloggers repeat on their sites. Egypt will be liberated. You can try to block Facebook but you will still find us on the streets.

(Additional reporting by Marius Bosch in Johannesburg and Peter Apps in London; Editing by Edmund Blair and Myra MacDonald)