US President Barack Obama has strongly condemned the violence against Egyptian civilians, and has cancelled joint military exercises.
He said force was not the way to resolve political differences.
Mr Obama’s comments come a day after security forces broke up the protest camps of Muslim Brotherhood supporters, leaving at least 500 people dead.
Brotherhood members had been protesting for weeks about the army’s overthrow of President Mohammed Morsi in July.
In the latest violence on Thursday, hundreds of Brotherhood members set fire to a government building near Cairo.
Local TV footage showed firefighters evacuating employees from the building – which housed the offices of the Giza local government.
State-run Nile News TV also reported clashes between Brotherhood members and residents in a suburb of Alexandria.