President Hosni Mubarak has called out the army and declared a nationwide curfew in Egypt, as thousands of street protesters demand his ouster.
Tanks were sent on the streets of Cairo on Friday night after another day of prayers and protests.
Eight people are dead and nearly 900 reported to be injured.
The headquarters of the governing National Democratic Party in Cairo are
on fire.
Protesters also tried to force their way to the parliament building in Cairo, but riot police forced them back.
A 6pm - 7am curfew in Cairo, Alexandria and Suez announced by state television has been extended nationwide.
But people were still on the streets of Cairo and Alexandria after the curfew went into effect, with protesters urging the army to join them.
Witnesses in Suez say protesters overran a police station, seized weapons and set fire to security force vehicles.
The demonstrations, inspired by events in Tunisia, have swelled into the largest uprising in Egypt in three decades.
State television said President Mubarak decreed the curfew to stop riots, lawlessness and attacks on property.
Dozens of people were wounded earlier in the day when security forces fired rubber bullets, tear gas and water cannon at crowds and baton charged them.
In Cairo, police used tear gas and water cannons to disperse the crowds, who responded after Friday prayers by throwing stones.
The BBC reports internet and phone services - both mobile and landline - are disrupted.
The protests began on Tuesday against unemployment, corruption and rising prices.
Imams at state mosuqes told their congregations at Friday prayers not to go out into the streets again, but this did not work.
Rubber bullets used at mosque
Earlier, police fired rubber bullets at thousands of protesters who gathered outside a prominent mosque in central Cairo after Friday prayers.
The crowd threw stones at police lines and shouted slogans against President Mubarak. They want an end to his 30-year rule.
They shouted "down, down with Mubarak" and "the people want the regime to fall".
Riot police fired teargas and water canon to disperse them.
Nobel Peace Prize winner Mohamed ElBaradei, who has just returned to Egypt, says the people's fear has been broken and nothing will stop them now.
The BBC reports the demonstrations were held in several cities: Suez, Alexandria, Mansoura and Aswan, as well as Minya and Assiut south of Cairo, and al-Arish in the Sinai peninsula.
The Muslim Brotherhood earlier said it would back the protests of Friday.
At least seven people have died and up to 1000 have been arrested since the protests began on Tuesday.
Lead from Tunisia
The unrest follows an uprising in Tunisia two weeks ago, in which President Zine al-Abidine Ben Ali was toppled.
Mr Mubarak, 82, has been in office since 1981. The Egyptian government tolerates little dissent and demonstrations are outlawed.
On Thursday, the National Democratic Party said it was ready for dialogue but did not offer any concessions.
The United States, Britain and Germany have expressed concern about the violence.
US Secretary of State Hillary Clinton says Egypt should restrain its security forces and allow peaceful protests.
Britain noted the protesters have legitimate grievances.
