Tensions are growing in Egypt as anti-government protests continue despite a government crackdown.
Demonstrators took to the streets across the country on Wednesday, following Egypt's largest public protests in modern history in Cairo the day before.
A video posted online showed protesters occupying a subway station in Cairo. Incoming trains were forced to a halt after demonstrators climbed onto the tracks.
Another online video showed protesters setting fire to a government building and throwing fire bombs at the headquarters of the ruling National Democratic Party in Suez, east of Cairo.
In Alexandria, Egypt's second largest city, demonstrators also reportedly clashed with security forces.
Authorities say four citizens and two police officers were killed and many others injured during the two days of unrest. About 1,000 people were arrested nationwide.
On Thursday, no new disturbances were reported in Cairo. But messages on social networking sites urged people to come out in force after Friday prayers. Police are bracing for the possibility of more unrest that day.
President Hosni Mubarak has ruled Egypt with a heavy hand for 30 years. Dissent is barely tolerated -- before parliamentary elections in November, the government arrested more than 1,200 opposition members and cracked down on the media.
Speculation that the 82-year-old Mubarak may let his son run in a presidential election this fall has led to accusations of nepotism. Rampant inflation and high unemployment, especially among college graduates, have increased dissatisfaction among the people.
It is believed that the recent collapse of Tunisia's autocratic government following nationwide protests may have spurred the discontented Egyptian public into action.