Nearly 150 people rallied late Friday in Cairo's iconic Tahrir Square in favour of a "civil state" after a visit by Egypt's ruling general, Field Marshal Hussein Tantawi.
"Civil, civil" and "down with military rule" they chanted.
Some carried a huge Egyptian flag, an AFP reporter witnessed.
Military and anti-riot police, already present in large numbers during the day, received reinforcements at sundown.
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Brief clashes erupted as demonstrators pelted police with stones and water bottles prompting a response in kind.
But calm quickly returned as a group of demonstrators intervened chanting "Peaceful, peaceful. The army and the people are a single hand."
The protest unfolded after iftar meal that breaks the daytime fast during the month of Ramadan.
The demonstration in favour of a civil state came as a counter to a July 30 rally that drew hundreds of thousands of Islamists to Tahrir in a show of support for what they called "Egypt's Islamic identity."
Dozens of groups had called for rallies marking a "Friday of love for Egypt" but they decided to postpone the gathering to "be better prepared," local press reported, although some of them decided to observe iftar.
Tantawi earlier in the day inspected military police deployed in Tahrir square, epicentre of the January-February revolt that toppled president Hosni Mubarak.