The U.S. Embassy in Cairo told its citizens in Egypt to consider leaving the country as soon as possible, and said it had authorized the voluntary departure of dependents 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 armored vehicles onto 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 antagonizing protesters.
The demonstrators from all segments of Egyptian society have taken to the streets for nearly a week calling for President Hosni Mubarak to step down. Mubarak named his intelligence chief Omar Suleiman to the new role of vice president on Saturday but many protesters said they wanted the complete removal of an administration they blame for poverty, unemployment, widespread corruption and police brutality.
The army appeared to be taking tougher action on some streets by early Sunday afternoon.
At Tahrir Square in the heart of Cairo, two soldiers standing guard next to a tank were working with several young men in civilian clothes to check the IDs and bags of hundreds of arriving protesters.
They found a kitchen knife hidden in a plastic bag carried by a man in his 20s as he attempted to enter the square. The soldiers wrestled the man to the ground, beat him and put him inside their tank.
Some 4,000 protesters chanted slogans against Mubarak in the square, the main gathering point for protesters since anti-government demonstrations began Tuesday, emboldened by Tunisians' success in driving out their president earlier in the month.
Army helicopters were flying low over Cairo and entire neighborhoods remained without any troops two days after Mubarak called the army out on the streets. But many Cairo neighborhoods and other parts of the country remain untouched by looting or street crime.
President Barack Obama met with security aides Saturday afternoon and issued a plea for government restraint in Egypt, where Washington has long feared increasing influence by Muslim militants.
Egyptian security officials said that overnight armed men fired at guards in gun battles that lasted hours at the four prisons including one northwest of Cairo that held hundreds of militants. The prisoners escaped after starting fires and clashing with guards.
Those who fled included 34 members of the outlawed Muslim Brotherhood, Egypt's largest and best organized opposition group. The Muslim Brotherhood's lawyer, Abdel-Monaem Abdel-Maqsoud, told The Associated Press the 34 were among scores rounded up by authorities ahead of the large anti-government demonstrations on Friday. The escapees included at least seven senior members of the group.
The Egyptian security officials said several inmates were killed and wounded, but gave no specific figures. They spoke on condition of anonymity because they were not authorized to share the information with the media.
Looting and arson continued until dawn as the police totally disappeared from the streets of the capital and several major Egyptian cities. There was no explanation for why the police vanished.
The vacuum left by their melting away has prompted residents to form neighborhood protection groups, armed with firearms, sticks and clubs. The citizens set up self-styled checkpoints and barricades and used bricks and metal traffic barriers to block off side streets.
Groups of youths also directed traffic in parts of Cairo, chasing away the gangs of criminals smashing passing cars. Residents said gangs were also stopping people on the streets and robbing them.
In the upscale neighborhood of Zamalek, long lines formed at shops and grocery stores as Egyptians tried to stock up on food, water and other supplies. Stores appeared to be running short of most items, especially bottled water. At one store, water was selling for three times the normal rate.
State Egyptian television, meanwhile, said authorities have decided to close down the Cairo offices of the Qatar-based Al-Jazzera television and suspend the accreditation of its reporters.
The Egyptian TV did not give a reason for the move, but Egyptian authorities have often in the past charged that the station's coverage of events in Egypt was sensational or biased against Mubarak's regime.