The United States updated its travel warning to Egypt late Friday and said non-emergency diplomatic staff could leave the country, after an American was among two people killed in protests.
"The Department of State authorized the departure of a limited number of non-emergency employees and family members," it said in the updated warning.
It cautioned US citizens "to defer non-essential travel to Egypt at this time due to the continuing possibility of political and social unrest."
"US citizens are urged to remain alert to local security developments and to be vigilant regarding their personal security."
The warning came after an American was among two people killed in Egypt's second city of Alexandria as clashes erupted Friday during rival demonstrations for and against Islamist President Mohamed Morsi a year after his election.
The US citizen, a 21-year-old who reportedly worked for an American cultural center in the northern port city, was killed as he took photographs of a demonstration, officials said.
"We have heard of reports of the death of a US citizen. We are seeking to confirm," an official at the US embassy in Cairo told AFP.
The travel warning made no mention of Friday's reported death, but highlighted that a private US citizen was stabbed outside the embassy in Cairo on May 9 after being asked if he was American.
The State Department warned that "political unrest ... is likely to continue in the near future due to unrest focused on the first anniversary of the president's assumption of office."
"Demonstrations have, on occasion, degenerated into violent clashes between police and protesters, resulting in deaths, injuries and extensive property damage," it added.
"Participants have thrown rocks and Molotov cocktails and security forces have used tear gas and other crowd control measures against demonstrators. There are numerous reports of the use of firearms as well."
The notice stressed, however, that the US embassy, which is very close to Cairo's Tahrir Square, remained open and noted that the tourist areas including Luxor, Aswan and Red Sea resorts like Sharm el-Sheikh remained calm.