CAIRO – Gangs of armed men attacked at least four jails across Egypt before dawn Sunday, helping to free hundreds of Muslim militants and thousands of other inmates as police vanished from the streets of Cairo and other cities.

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.

Turkey was evacuating about 750 citizens and the Chinese government warned against travel to Egypt. Private tour groups and corporations began trying to evacuate their clients and expatriate employees. But dozens of flights were canceled and delayed and crowds filled Cairo International Airport, desperate and unable to leave.

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. Banks were closed on orders from Egypt’s Central Bank, and the stock market was shut on what is normally the first day of the trading week. Markets across the Middle East dropped on fears about the instability’s damage to Egypt’s economy, and the region’s.

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, 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.

Ahmed Shafiq, the outgoing civil aviation minister and Mubarak fellow former air force officer, was named prime minister.

Many protesters said Sunday 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.”

The army appeared to be taking tougher action on the streets by early Sunday afternoon — and were coordinating with protesters.

At Tahrir Square in the heart of Cairo, where Riyad and tens of thousands of other protesters were marching, two military armored vehicles blocked the entrance, and soldiers working with civilian protester volunteers were checking IDs and bags of people arriving to join the marches. The soldiers and volunteers said they were searching for weapons but also looking to make sure plainclothes police did not enter the square.

“The army is protecting us, they won’t let police infiltrators sneak in!” one volunteer shouted to the crowds lining up to get in. Inside the square, protesters chanted, “The army and the people are one joined hand!”

The soldiers also 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.

Egyptian security officials told The Associated Press that army troops were hunting for the escaped prisoners, in some cases with the help of the police. State television also showed footage of what it said was dozens of prisoners recaptured by the army troops, squatting on dirt while soldiers kept watch over them.

State Egyptian TV showed footage of Mubarak during what it said was a visit to the country’s military command center. Mubarak looked somber and fatigued in his first public appearance since he addressed the nation late Friday to promise reform and annouce the dismissal of his Cabinet.

The brief footage appeared designed to project an image of normalcy.

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.

An unprecedented Internet cutoff remained in place after the country’s four primary Internet providers stopped moving data in and out of the country early Friday in an apparent move by authorities to disrupt the organization of demonstrations.

Egyptian mobile networks were back up but with text-messaging widely disrupted. Blackberry Messenger and Internet services were operating sporadically.

The American University of Cairo has delayed the Sunday start of the semester a week because of the ongoing unrest, spokeswoman Rehab Saad. The Iraqi government offered to evacuate citizens for free.

“We will send whatever planes are needed to those who want to leave Egypt,” Transportation Ministry spokesman Aqeel Hadi Kawthar told The Associated Press in a telephone interview. “It will be free of charge.”

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.

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Sarah El Deeb and Diaa Hadid contributed to this report.