A South African AIDS activist was raped and killed after she told her rapists that she was HIV positive, police said on Saturday.

The police said the incident took place outside a tavern in the township of Khayelitsha in Cape Town where 21-year-old Lorna Mlosana was sitting with a friend.

Five men followed Mlosana, an activist for Treatment Action Campaign, when she went to the tavern toilet.

The men overpowered and took turns in raping her, the police said.

When the friend tried to rescue her, she was also severely beaten up.

A spokesperson for TAC, Vuyiseka Bubula, said the men became angry after Mlosana told them that she was HIV positive and that they would contract the disease.

"The men then went berserk and began beating her up. They ran away from the tavern after they realised that they had killed Mlosana," she said.

The police said they were following leads and would make arrests soon.

The murder came a few days after the government launched a 16-day campaign against violence against women and children.

It was also the second such incident in four years. In 1999, a Durban AIDS activist, Gugu Dlamini, was stabbed by a group of young men in the local township of KwaMashu after she revealed at a meeting that she was HIV positive.