"Due to the security situation in the vicinity of the U.S. Embassy, our public services will be closed ... Tuesday ... including visa services and the Information Resource Center," the embassy said in a statement.
Emergency services for American citizens will be offered "to the extent possible," the statement added.
At least 128 people, including 48 security officers, were injured in overnight clashes that continued into Tuesday morning in Kafr al-Sheik, the MENA news agency reported.
Two officers and 14 recruits were hurt by stones thrown during protests, while another 30 people, including recruits and protesters suffered breathing problems brought on by tear gas.
Six protesters were arrested.
Some 51 people have died in the violence since Friday, the Health Ministry said Sunday, Egypt Independent reported.
The ministry said Monday the death toll from rioting in Port Said had risen from 37 to 40 after three people died in the hospital from their injuries.
Cairo suffered its first fatality from the disturbances early Monday when a passerby was hit by birdshot in Tahrir Square.
The leader of Egypt's army Tuesday warned of the collapse of the state if political forces failed to reconcile.
"The continuation of the conflict between different political forces and their disagreement on running the affairs of the country may lead to the collapse of the state and threatens the future of the coming generations," said Gen. Abdul-Fattah al-Sisi, who also serves as defense minister.
Sisi, quoted on the army's Facebook page, also said an attempt to influence the stability of the state institutions "is a dangerous matter that harms Egyptian national security," The New York Times reported.
The worst of the turmoil was in Port Said, which has seen 45 deaths in three days, where Egyptian President Mohamed Morsi imposed a month-long state of emergency, calling on the army to regain control of security.
The state of emergency, also declared for two other cities in the Suez Canal zone, all but eliminates due process, letting police investigate, arrest and detain suspects without trial.
State-run media said anti-government protesters ignored Morsi's curfew and clashed with police and troops, state-run media reported Tuesday.
"He declared a curfew, and we declare civil disobedience," one person attending a funeral Monday in Port Said told the Times.
Thousands of Egyptians across the country defied the clampdown and took to the streets within 20 minutes after the nighttime curfew Monday, CNN said.