"Down, down, Hosni Mubarak," a group of more than 200 chanted as they tried to gather in central Cairo's Tahrir Square. Police hauled away a group of about a dozen protesters, shouting "freedom, freedom" near parliament, minutes later.
Hundreds of riot police were also stationed across the capital, encircling small groups of protesters as they gathered to converge on the centre.
Police beat some with sticks and dragged dozens away, witnesses said. They also chased off reporters and seized cameras being used by media trying to cover the protest.
Plain-clothed policemen detain a protestor. (Photo: AFP)
Such demonstrations are rare in Egypt, an important US ally in the region, and are usually swiftly quashed by security forces.
"We are seeking to do away with injustice and other bad things," screamed Meena Samir, a student at Cairo University.
Call for political freedom
The pro-reform group behind the protest, the Sixth of April Youth, is seeking constitutional amendments and an end to an emergency law that sanctions indefinite detentions. Egypt holds a parliament election this year and a presidential vote in 2011.
Mubarak's National Democratic Party is expected to win an overwhelming majority in parliament. But human rights groups, which have long complained of manipulation of Egyptian voting, are calling for international oversight of the elections.
Mubarak, 81, has not said whether he will run for a sixth presidential term but, if he does not, many Egyptians believe he will try to hand power to his politician son, Gamal, 46.
Rules outlined in the constitution make it almost impossible for any candidate to mount a realistic challenge for the presidency without the backing of Mubarak's ruling party.
"What we are calling for is political freedom for Egyptians through peaceful means. Our aim is to instigate political movement among the people to demand their rights," Omar Ali, a April 6 movement organiser, told Reuters before the protest.
'Shows fear of ruling party'
One group of more than 20 protesters that included opposition politician Ayman Nour, who came a distant second in the 2005 presidential race, was blocked by security from reaching the square, witnesses said.
A security source said about 60 people had been detained in central Cairo for demonstrating without a permit. Men in plain clothes with guns in holsters hauled some demonstrators away.
"If they want to take people, they have to do it in a civilized way. Nobody has a weapon... We are trying to express our opinion," said Salma Gaafar, one young protester.
After the protest, April 6 leader Ahmed Maher said the group would file a lawsuit against the Interior Ministry. "This shows the fear of the ruling (party) of any opposition - despite its claims that it allows democracy," he said.
Earlier on Tuesday, police detained seven students as they headed to central Cairo from Helwan University on Cairo's outskirts. Sixteen students were held as they made their way into the city from south of Cairo, a security source said.
The Arabic satellite channel Al-Jazeera reported that Egyptian police confiscated tapes from one of its TV crew covering the demonstrations in Cairo.
The April 6 group, formed after protests over surging prices in 2008 turned violent, and another group called Kefaya (Enough) are Egypt's two active anti-government movements. The main political opposition group, the Muslim Brotherhood, has a minority in parliament but has tended to avoid street protests.
Tuesday's march was supported by Nour's liberal Ghad (Tomorrow) opposition party.