Police fired tear gas in the Sudanese capital on Monday when clashes between pro-government university students and their opponents spilled onto a downtown street, witnesses said.
"Both sides had steel bars, stones and chains and some of them clashed outside campus," said one student witness at the University of Khartoum.
Riot police then intervened with tear gas, he said, declining to be named.
The clashes occurred between students who back the ruling National Congress Party and "opposition students", many of them from the Darfur region, the witnesses said.
An AFP reporter later found stones littering the street outside the campus. Riot police still stood by in the area.
A similar confrontation occurred at the university on Sunday night, students said, with varying estimates of the number wounded.
Tensions have persisted for more than two years at the campus, which has been periodically shut down and was the starting point for anti-government protests in 2012.
The university had recently reopened after its latest closure following the death in March of a student during a University of Khartoum rally for peace in the war-torn Darfur region.