The Egyptian military has moved in to break up street battles between supporters and opponents of deposed Egyptian President Mohamed Morsi.
Armored vehicles moved across the 6th of October Bridge in central Cairo on Friday with anti-Morsi protesters hanging on.
A military spokesman tells the French news agency that soldiers are not taking sides but are moving in to protect lives.
Members of the rival camps fought across Cairo and other cities including Alexandria Friday, throwing rocks and fireworks and engaging in fistfights. State-run television says at least 17 people have been killed.
The United States and the United Nations urged Egyptians to reach a peaceful end to the crisis and avoid violence.
U.N. Secretary General Ban Ki-moon said, "This is a critical juncture in which it is imperative for Egyptians to work together to chart a peaceful return to civilian control, constitutional order, and democratic governance."
In Washington, State Department spokesperson Jen Psaki said the United States calls on "all Egyptian leaders to condemn the use of force and to prevent further violence among their supporters."
Earlier Friday, government troops opened fire on Morsi supporters who tried to march on the Defense Ministry headquarters.
The army arrested Morsi and other leaders of the Egyptian Muslim Brotherhood on Wednesday and suspended the constitution. The army said its action was prompted by the risk of a popular uprising.
The military has sworn in a senior jurist, Adly Mansour, as interim president.
The opposition has accused Morsi of betraying the 2011 revolution that toppled Hosni Mubarak.
The military and Egypt's former opposition groups have called for reconciliation as the military moves forward with its so-called road map to restore democratic civilian rule.
Muslim Brotherhood leaders have slammed the military for shutting down its official television channel and newspaper and several other Islamist media outlets. The group said in a statement that the moves bring Egypt "back to the era of repressive practices, dictatorship, and corruption."
Judicial officials say they will open an investigation next week against Morsi and other Brotherhood members on charges of "insulting the judiciary."
"We are not in a battle with the Egyptian armed forces; our battle is with those who orchestrated the coup, until they go back on it and free President Morsi from his captivity and restore him to the presidency," said Mohammed el-Beltagy, General Secretary of the Islamist Freedom and Justice Party.
Muslim Brotherhood supporter Safwat Hegazy said the group hopes to overwhelm the military by the sheer force of numbers.
"This is the Egyptian people's million man march to regain legitimacy from the traitors, from the military council," said Hegazy.
A military attack helicopter flies near the presidential palace in Cairo, Egypt, Friday, July 5, 2013.
Supporters of former Egyptian President Mohamed Morsi carry an injured man during clashes outside the Republican Guard building in Cairo, July 5, 2013.
Supporters and opponents of Egypt's Islamist President Mohamed Morsi clash in Cairo, July 5, 2013. Tens of thousands of Islamists streamed across a Nile River bridge toward Tahrir Square, threatening a showdown moments after the top leader of the Muslim Brotherhood defiantly spoke before a cheering crowd of supporters, vowing to reinstate the ousted president and end military rule.
Islamist protesters, one holding a picture of ousted president Mohamed Morsi, hold up blood-stained hands after troops opened fire on a protest in front of the Republican Guard headquarters in Nasr City, Cairo, July 5, 2013
Opponents of Egypt's Islamist ousted president Mohamed Morsi wave national flags as they celebrate in Tahrir Square, in Cairo, July 5, 2013
Protesters who support former Egyptian President Mohamed Morsi gather around the body of a man during clashes outside the Republican Guard building in Cairo, July 5, 2013.
A protester, who supports former Egyptian President Mohamed Morsi, chants slogans during a rally near Cairo University after Friday prayers in Cairo, July 5, 2013.
Security forces watch over supporters of former Egyptian President Mohamed Morsi during clashes outside the Republican Guard building in Cairo, July 5, 2013.
A protester who supports former Egyptian President Mohamed Morsi offers flowers to military personnel during clashes outside the Republican Guard building in Cairo, July 5, 2013.
Supporters of former Egyptian President Mohamed Morsi gather around the covered body of a victim of clashes outside the Republican Guard building in Cairo, July 5, 2013.
Supports of former Egyptian President Mohamed Morsi run during demonstrations outside the Republican Guard building in Cairo July 5, 2013.
A protester, who supports former Egyptian President Mohamed Morsi, holds up a copy of the Koran as she and others march near Cairo University after Friday prayers in Cairo, July 5, 2013.
Supporters of ousted Egyptian President Mohamed Morsi react to an explosion of unknown origin and throw stones at police officers nearby, during a protest in Cairo University, Giza, Egypt, July 5, 2013.
A supporter of ousted Egypt's President Mohamed Morsi cries during a protest near the University of Cairo, Giza, Egypt, Friday, July 5, 2013. Arabic reads, "Yes for the legitimacy." Egypt's Muslim Brotherhood called for a wave of protests Friday, furious over the military's ouster of its president and arrest of its revered leader and other top figures, raising fears of violence and retaliation from Islamic militants.
Opponents of Egypt's ousted president Mohamed Morsi wave national flags and posters showing Lt. Gen. Abdel-Fattah el-Sissi in Tahrir Square, in Cairo, Egypt, Friday, July 5, 2013. Egypt's Muslim Brotherhood called for a wave of protests Friday, furious o