Sudanese police fired tear gas on hundreds of people who gathered to protest in central Khartoum for the second day on Thursday over the killing of a student at a campus demonstration a day earlier.
"Killing of a student, killing of a nation, down with military rule," the protesters chanted.
Protests in Sudan are usually limited to campuses and Thursday's demonstration was unusual in that it took place in the centre of the capital.
Clashes also erupted later at another protest by hundreds in front of Khartoum University. Police used batons and students hurled rocks.
Students had initially demonstrated on Wednesday against government plans to sell off Khartoum University buildings before gunmen in plain clothes opened fire on them, killing 20-year-old Mohammed al Sadek.
His funeral later in the day turned into an anti-government protest by students, witnesses said.
President Omar Hassan al-Bashir, who took power in a 1989 coup, brooks little dissent in Sudan, which has been suffering from an economic crisis since South Sudan seceded in 2011, costing Khartoum more then 70 percent of its oil revenues.
Bashir is wanted by the Hague-based International Criminal Court on charges of masterminding genocide, crimes against humanity and war crimes during Sudan's Darfur conflict. He denies wrongdoing.
Last week Amnesty International called for a thorough and impartial investigation into violent attacks against students after an 18-year-old student was shot dead.
Intelligence agents killed Abubakar Hassan Mohamed Taha in North Kordofan on April 19 when they fired on marchers who had intended to submit a list of opposition candidates for university elections, the group said.