Smoke hangs in the air after police used stun grenades in an attempt to disperse protesters outside the University of Johannesburg in Soweto during US President Barack Obama's visit. Picture: Dylan Martinez

Johannesburg – Police officers on Saturday fired a stun grenade at a group of protestors near the entrance of the University of Johannesburg Soweto campus ahead of US President Barack Obama's visit there.

Spokeswoman Sally de Beer said about 120 protestors gathered about 400 metres from the gates to the campus.

The group were allowed permission to protest, but only until 2pm.

“When their time lapsed at 2pm, they refused to comply with a request to disperse as they were required to ...the police fired one stun grenade and they then dispersed,” de Beer said.

No arrests were made.

De Beer said: “We totally respect everyone's right to demonstrate peacefully, but if they are required in terms of their permission to protest, they must stick to the requirements.”

Obama was due to address young people at an event at the Soweto campus. – Sapa