South Africa's police minister has defended officers after robberies at a concert in Johannesburg, reports AFP news agency.

People have tweeted reports of stabbings and robberies as people left the Global Citizen Festival which was marking 100 years since Nelson Mandela's birth.

People on Twitter had criticised the police for not being there to protect the concert goers as they left the festival.

But AFP quotes police minister Bheki Cele as saying the chaos was the organisers' fault:

"There is no need to blame South African police that there was no Uber, there was no transport and all that - that should be asked from the organisers," AFP reports him as saying.

Global Citizen, which organised the event, said in a statement that "after such an inspiring evening, we are saddened to hear the challenges people had while leaving the venue". "We have been working to support people getting home safely," it said.