Internet access has been shut down across Egypt as demonstrations against the 30-year rule of President Hosni Mubarak continue.
Mass protests have been staged since Tuesday by people emboldened by this month's revolt that toppled the authoritarian leader in Tunisia.
Early on Friday, Egyptian demonstrators fought security forces in the city of Suez.
"This is a revolution," one 16-year-old protester said, "Every day we're coming back here."
As well access to the internet, mobile phone text messaging services have been affected and appeared to be partially disabled.
Activists are replying on the web, especially social media services like Twitter and Facebook, to organise their protests.
US based Internet monitoring firm, Renesys, said the total shut-down of the Internet it recorded early on Friday was "unprecedented in Internet history", going far beyond measures taken during Tunisia's protests or a 2009 uprising in Iran.
"Renesys observed the virtually simultaneous withdrawal of all routes to Egyptian networks in the Internet's global routing table," it said. "The Egyptian government's actions have essentially wiped their country from the global map."
The United States is Egypt's close ally and major donor, and has tread carefully over unrest in a country it considers a bulwark of Middle East stability.
Nobel Peace Prize winner Mohamed ElBaradei, who returned to Egypt from Vienna on Thursday, has called for Mubarak to resign and said he would join the protests on Friday.
A page on Facebook listed more than 30 mosques and churches where protesters are expected to gather.
"Egypt's Muslims and Christians will go out to fight against corruption, unemployment and oppression and absence of freedom."
In Suez, which has been the centrepoint for some of the most violent demonstrations, police fired tear gas at protesters who hurled stones and petrol bombs overnight. Fires burned in the street, filling the air with smoke.
The city fire station was ablaze. Waves of protesters charged towards a police station deep into the night. Demonstrators dragged away their wounded comrades into alleys.
Security forces shot dead a protester in the north of the Sinai region on Thursday, bringing the death toll to five.