'Police will stay vigilant'
The police and other law enforcement agencies had maintained law and order in the Johannesburg CBD as ANC Youth League president Julius Malema attended a disciplinary hearing, police said.
"There were no disruptions except a few incidents of stone throwing," Lt-Col Lungelo Dlamini said in a statement.
"Police used minimum force by using a water cannon to manage the situation. Only one police officer sustained a head injury when he was hit by a stone thrown from the crowd," he said.
Police had recorded footage that could be used to identify the stone throwers after which they would be arrested and charged with attempted murder and public violence.
The gathering was also monitored on the city's closed-circuit television cameras.
Only one person was arrested as groups of people in support of Malema threw half- bricks, stones and bottles in the city centre, and set alight bins and T-shirts.
Objects were thrown at at at least five journalists, including Sapa photographer Werner Beukes, and a cable was stolen from eNews.
Dlamini said that police were on the ground throughout the night yesterday to maintain law and order.
Johannesburg metro police spokesman Chief Superintendent Wayne Minnaar said the man arrested was shown tipping over a dustbin on CCTV.
Dlamini said that there had been no application for permission for the gathering, so in terms of the law, police were required to maintain law and order.
Earlier, in Cape Town, Police Minister Nathi Mthethwa announced the approval of a new policy for police to manage protests. It called for a dedicated National Public Order Policing Unit within the police.
In the 1970s, the SA Police introduced riot control units to deal with the large-scale unrest that was part of the struggle against apartheid.