CAIRO -- Thousands of backers and opponents of Egypt's Islamist president held competing rallies in the capital Friday and new clashes erupted between the two sides in the country's second largest city, Alexandria, in a prelude to massive nationwide protests planned by the opposition this weekend demanding Mohammed Morsi's removal.
For the past several days, Morsi's opponents and members of his Muslim Brotherhood have battled it out in the streets of several cities in the Nile Delta in violence that has left at least five dead. The latest died Friday from injuries suffered in fighting the day before, security officials said.
Many fear the clashes are a sign of more widespread and bloodier battles to come on Sunday, the anniversary of Morsi's inauguration, when the opposition says it will bring millions into the streets around the country.
"We must be alert lest we slide into a civil war that does not differentiate between supporters and opponents," warned Sheik Hassan al-Shafie, a senior cleric at Al-Azhar, the country's most eminent Muslim religious institution.
The Cairo International Airport was flooded with departures, in an exodus airport officials called unprecedented. They said all flights departing Friday to Europe, the United States and the Gulf were fully booked with no vacant seats.
Many of those leaving were families of Egyptian officials and businessmen and those of foreign and Arab League diplomats -- as well as many Egyptian Christians, the officials said, speaking on condition of anonymity because they are not authorized to talk to the press.
In the Mediterranean city of Alexandria on Friday, scuffles erupted between Morsi's supporters and opponents, near the local headquarters of the Muslim Brotherhood.
The fighting began when thousands of anti-Morsi protesters marched toward the Brotherhood headquarters, where up to a 1,000 supporters of the president were deployed, protecting the building. Someone on the Islamist side opened fire with birdshot on the marchers and the two sides began to scuffle, according to an Associated Press cameraman at the scene.
Nine people were wounded by birdshot, Deputy Health Minister Mohammed al-Sharkawi told AP.
Security forces fired tear gas at the Brotherhood supporters, but when the two sides continued battling, they withdrew.
Each side insists it is and will remain peaceful on Sunday -- and each has blamed the other for the violence so far.
Tamarod, the activist group whose anti-Morsi petition campaign evolved into Sunday's planned protest, said in a statement it was opposed "to any attack against anybody, whatever the disagreement with this person was," and accused the Brotherhood of sparking violence to scare people from participating Sunday.
Tamarod says it has collected nearly 20 million signatures in the country of 90 million demanding Morsi step down.
The Brotherhood says the five killed in the Delta clashes were its members. Some people "think they can topple a democratically elected President by killing his support groups," Gehad el-Haddad, a Brotherhood spokesman, wrote on his Twitter account.
In Cairo, thousands of Morsi backers filled the street outside the Rabia el-Adawiya Mosque in Cairo, not far from the presidential palace. The palace -- one of the sites where the opposition plans to hold rallies Sunday -- has been surrounded by concrete walls.
In his Friday prayer sermon, the cleric of Rabia el-Adawiya warned that if Morsi is ousted "there will be no president for the country" and Egypt will descend into "opposition hell."
Outside in the street, the Islamists chanted religious slogans. "It is for God, not for position or power," they shouted. "Raise your voice strong, Egyptian: Islamic Shariah." Many wore green headbands with the slogans of the Muslim Brotherhood.
Across the city, thousands of Morsi opponents massed in Cairo's central Tahrir Square, shouting for the president to "leave, leave."
Violence erupted in several parts of the Delta, north of Cairo.
At least six people were injured when an anti-Morsi march was attacked by the president's supporters in the city of Samanod, according to a security official. Attackers fired gunshots and threw acid at the protesters as they passed the house of a local Brotherhood leader, the official said.
In the Delta city of Tanta, four unidentified men believed to be Morsi supporters tried to attack a mosque preacher during his sermon, in which he called on worshippers to stand with Al-Azhar's calls to avoid bloodshed.
Hundreds of protesters in the nearby city of Bassioun hurled stones at the local headquarters of the Brotherhood's Freedom and Justice Party. They tore down the party's sign and crushed it, security officials said.
Security officials say three people have died in the past three days in Nile Delta city of Mansoura, along with two others in the nearby province of Sharqiya.
In Sharqiya on Thursday, an Islamist march encountered an anti-Morsi march, leading to scuffles that evolved into full-fledged battles, the officials said. The two sides hurled stones at each other and fired gunshots, and at least 70 were injured.
The officials spoke on condition of anonymity because they were not authorized to talk to the press.