CAIRO, Egypt (CNN) -- Egyptian troops canvassed streets Friday after a fresh spate of violence in the volatile North African nation, hoping to prevent a repeat of the bloody, chaotic revolution of two years ago, a military spokesman said.
Military forces have been deployed nationwide to protect Egyptian citizens and property, Ahmed Ali told the MENA state news organization, as reported by Ahram Online, another official news agency. The Ahram story recalled how police stations came under attack, prisons were broken into and shops were looted in the unrest of early 2011.
"These measures are being taken to avoid a January 28, 2011, scenario," the spokesman said. Those protests and a government crackdown culminated in the ouster of longtime Egyptian President Hosni Mubarak.
Friday's move follows deadly clashes in Alexandria and elsewhere, many of them targeting Egypt's Muslim Brotherhood.
Four members of that Islamist group -- which was banned under Mubarak but has risen to power since his fall, most notably in the form of President Mohamed Morsy who has been in office for a year -- have been killed in recent days.
The Alexandria office of the Brotherhood's political arm, the Freedom and Justice Party, was attacked Friday. Health Ministry spokesman Yehya Moussa said one man was killed by a gunshot wound to the head during clashes outside party headquarters.
And on Friday night, he said that a 21-year-old American had died in the Alexandria clashes.
The young man's family identified him as Andrew Driscoll Pochter, a Kenyon College student living in the Egyptian port city to teach English to 7- and 8-year-old children. Their understanding was that he'd been witnessing the events "as a bystander (when he) was stabbed by a protester."
"He went to Egypt because he cared profoundly about the Middle East, and he planned to live and work there in the pursuit of peace and understanding," his family said. "Andrew was a wonderful young man looking for new experiences in the world and find ways to share his talents."
State media reported that 70 were injured in the same clashes.
Two people were shot dead Thursday when armed men attacked the Muslim Brotherhood officers in Zagazig, Morsy's hometown, spokesman Gihad Haddad said.
The identity of the shooters is unknown, but Haddad said witnesses heard the gunmen shouting "down with Morsy."
Another Muslim Brotherhood member died from injuries he suffered in clashes in Mansoura, Haddad said. Morsy gave a speech this week highlighting his achievements during his first year in office.
But the largest opposition umbrella group said Morsy did not address his shortcomings, and issued a statement calling for snap presidential polls, a new government and constitutional amendments.
Morsy's speech "only deepens our resolve to press our demands for early presidential elections in order to achieve the aims of the revolution, most important of which is social justice," the statement said.
Haddad said that the Brotherhood's policy is to never respond to attacks against it with violence. However, he seemed to suggest that the Brotherhood's leaders may not be able to stop reprisal attacks.
"I don't think organization will matter that much. I am concerned because, if anything, these killings are infuriating the youth. All the martyrs are Brotherhood youths," he said.
He said the Brotherhood would go ahead with planned demonstrations Friday in Cairo followed by an indefinite sit-in.
If the sit-in extends to Sunday, it would coincide with mass demonstrations planned by opposition factions in front of the presidential palace. Governments around the world are paying attention -- at the least, to make sure that their own workers and citizens are safe.
About 200 U.S. Marines in Sigonella, Italy, and Moron, Spain, have been put on alert as a precaution, according to two officials in President Barack Obama's administration.
The units have several V-22 tilt-rotor aircraft that could carry personnel and weapons to protect the U.S. Embassy and American government personnel and citizens if violence breaks out targeting Americans. They've been told to be ready to be airborne within 60 minutes of getting orders to deploy, the officials said.
The United States has approved the departure of embassy and consulate employees and their dependents because of the brewing unrest, a senior State Department official said. Nonessential employees and their relatives can get help leaving, if they choose to do so.