Protesters from the Kifaya (Enough) Movement, which has organised a number of demonstrations in Cairo against Husni Mubarak's rule, were on Tuesday prevented from holding a rally by riot police.
"Two people from the Kifaya group who tried to demonstrate on the streets in central Asyut were detained," a police official said.
Officials also said police detained three protesters when 2000 agitating students at Asyut's branch of al-Azhar university tried to move their protest outside campus.
Egyptian security forces do not interfere with protests inside universities but usually prevent or restrict demonstrations held in the streets.
Series of protests
A witness said about 20 Kifaya demonstrators, holding placards denouncing any new presidential term for Mubarak, were surrounded by hundreds of riot police.
Students and activists across Egypt have held a series of protests in recent months against a possible fifth six-year term for 76-year-old Mubarak or any attempt to install his son Jamal as president.
Mubarak is facing public pressure
to drop a fifth presidential term
Jamal has said he is not a candidate for the polls.
About 1000 students held another pro-reform demonstration inside Asyut University, but students remained inside campus grounds, and there were no detentions, the officials added.
Mubarak has proposed changing the constitution to abolish the old system of a referendum on a single candidate chosen in advance by parliament, which is dominated by the ruling party.
But opposition politicians say they are worried the ruling party will make the conditions for standing so restrictive that Mubarak would not face a serious challenge in the elections, which are expected in September.