South African riot police on Saturday fired stun grenades and rubber bullets to disperse hundreds of people in the township of Soweto protesting against US President Barack Obama's visit, police said.
Demonstrators burned US flags and portraits of Obama, who is on a three-nation tour of Africa, chanting: "Arrest Obama, not us" and "Whose country is this?"
Several bangs were heard as armed police tried to move the demonstrators away from a campus of the University of Johannesburg where Obama later addressed a town hall event.
The protesters had permission to stage a rally but over-stayed their allocated time.
"Police asked them to disperse, but they did not," police spokeswoman Sally de Beer told AFP. "So police used stun grenades and two rounds of reduced rubber (rubber bullets)."
A witness said at least two people suffered rubber bullet wounds, but police denied the claim. No arrests were made.
Police had to hold back some people as Obama's convoy drove into the campus.
Members of the South African Communist Party and anti-Israel groups held up posters depicting Obama with a moustache like that of Nazi leader Adolf Hitler.
"The message is clear. We want him to honour the promises he made when he became president, including things like the closing of Guantanamo Bay," 30-year-old protester Firoz Osman told AFP.
The university hosted a meeting between Obama and young leaders from all over Africa, as part of his message that it is time for a new generation to guide the continent into an era of democracy and prosperity.
Soweto is a sprawling township where riots sparked a nationwide struggle against the former racist apartheid regime.