Armed men who robbed a news team with South Africa's state broadcaster were caught in the act on the crew's own camera, the broadcaster said.

Journalist Vuyo Mvoko was seconds away from going on live television outside a hospital in Johannesburg, broadcaster SABC said.

Video footage showed two men accosting Mr Mvoko in the street as he was waiting to deliver his report to the camera with a microphone.

No weapon is visible in the SABC footage, but Mr Mvoko said one of the men threatened him with a gun when he did not immediately give up his mobile phone. The thieves took two or three phones and a laptop, he said.

The journalist said he and his team then called police.

Mr Mvoko was reporting from outside Milpark Hospital after reports that Zambian president Edgar Lungu was being treated there after travelling to South Africa for medical care.