A joint force of anti-riot police and army troops surrounded the entrance of the Jesuit Universite Saint-Joseph (USJ) on Wednesday where about 200 students from various Christian opposition groups were demonstrating, police said.
Hospital sources said three students were beaten and taken to hospital.
At least two others were detained, an AFP photographer on the scene said.
The demonstration was part of actions against the emigration of young Lebanese.
"The policy of the regime, the corruption and the dependence on Syria are at the base of the emigration of the youths," said student leader Sami Gemayel, representing the "Kataeb base" (a splinter group of the Christian party).
The movement of exiled leader General Michel Aoun, who opposes the presence of Syrian troops in Lebanon, denounced in a statement the "repression of the freedom of expression and the right to demonstrate guaranteed by international conventions and the Lebanese constitution."
The official Tele-Liban station said the security forces were enforcing a ban on street protests or gatherings until the end of municipal elections scheduled for May.