Gangs of armed men have attacked at least four jails across Egypt, helping to free hundreds of Muslim militants and thousands of other inmates as police vanished from the streets of Cairo and other cities.
The US Embassy in Cairo told its citizens in Egypt to consider leaving the country as soon as possible, and said it had authorised the voluntary departure of dependants and non-emergency employees, a display of Washington's escalating concern about the stability of its closest Arab ally.
The army sent hundreds more troops and armoured vehicles on to the streets of Cairo and other cities but appeared to be taking little action against gangs of young men with guns and large sticks who were smashing cars and robbing people.
At least one Nile-side shopping mall in Cairo was on fire after being looted the previous day.
The Arab world's most populous nation appeared to be swiftly moving closer to a point at which it either dissolves into widespread chaos or the military expands its presence and control of the streets.
A broader and tougher military role could be welcomed by increasingly fearful Egyptians but would run a risk of appearing to place the army on the side of the regime and antagonising protesters.
The demonstrators from all segments of Egyptian society have taken to the streets for nearly a week calling for President Hosni Mubarak, 82, to step down.
Mubarak named his intelligence chief, former army general Omar Suleiman, to the new role of vice president on Saturday, a move that perpetuated the overriding role of military men in Egyptian politics.
Many protesters said that they wanted the complete removal of an administration they blame for poverty, unemployment, widespread corruption and police brutality.
"If the president leaves today, chaos will be over," said schoolteacher Hussein Riyad. "People have been suffering for 30 years, a few days of horror don't matter."