The United States condemned clashes across Egypt on Friday and urged all leaders including the army to stop the violence after 14 people were killed following the toppling of president Mohamed Morsi.

"We condemn the violence that has taken place today in Egypt. We call on all Egyptian leaders to condemn the use of force and to prevent further violence among their supporters," State Department spokeswoman Jen Psaki said in a statement.

Tens of thousands of supporters of Morsi, who was deposed by the Egyptian military on Wednesday, protested across the country against his ouster.

In Cairo's Tahrir Square, at least two people were killed when Morsi supporters traded fire with his opponents, state television reported. The clashes subsided when the army separated the protesters using armored vehicles.

Violence between Morsi's supporters and opponents left one dead in Egypt's second city Alexandria and another in central Assiut, Egyptian officials said.

Violence also gripped other areas, including the Sinai where gunmen killed five policemen and Islamists killed a soldier in a machine gun and rocket attack.

"We expect the military to ensure that the rights of all Egyptians are protected, including the right to peaceful assembly, and we call on all who are protesting to do so peacefully," Psaki said.

"The Egyptian people must come together to resolve their differences peacefully, without recourse to violence or the use of force."

Washington is increasingly caught in a dilemma, not wishing to condone what could be seen as a military coup, while recognizing that the democratically elected Morsi had failed to bring in an inclusive government.