The rape of the 13-year-old, the latest such attack to 'cure' homosexuality, adds to calls for action – and retaliation

A 13-year-old lesbian has become the latest victim of "corrective rape" in South Africa, prompting activists to call for direct retaliatory action.

The girl, who is said to be open about her sexuality, was raped in Pretoria last Thursday, a government spokesman said.

Campaigners say so-called corrective rape, in which men rape lesbians to "cure" them of their sexual orientation, is on the increase in South Africa. Thirty-one lesbians have been killed because of their sexuality in the past decade, campaigners say, and more than 10 lesbians a week are raped or gang raped in Cape Town alone.

Last month, a 24-year-old woman who belonged to a gay and lesbian rights group was stoned to death after an apparent gang rape.

Officials said the 13-year-old victim's case is being investigated by police and she and her family are receiving support. Tlali Tlali, a government spokesman, said it seemed to be another incident of corrective rape, adding: "Government condemns this senseless and cowardly act of criminality."

Tlali said every South African had the right to express themselves in the sexual orientation of their choice. "Gay and lesbian rights are human and constitutional rights which must be protected and respected at all times."

Ndumie Funda, founder of the Luleki Sizwe Project, a charity that supports survivors of corrective rape in Cape Town, said she had heard reports of a transgender person being raped over the weekend. "It is getting worse and needs to come to an end," she said. "People are not being given a platform to come out of the closet. What about those who are locked in a cage and cannot come out? It's not fair and it's about time we talk."

Funda, 37, became involved in the campaign when she met Nosizwe Nomsa Bizana, who had been raped at gunpoint by five men and infected with HIV. The couple became engaged but Bizana died in 2007. Funda is forced to take a different route home every day to avoid being targeted because of her public activism.

She estimates about 510 women report corrective rape in South Africa each year and warned of a popular backlash. "It is about time we retaliate," she said.

Possible action includes disrupting imminent local elections. "We used to say during the apartheid era we will deal with them the way the enemy deals with us. The retaliation will be legitimated by the reaction of the people. I cannot give further details until I confer with the other comrades."

Last month, Noxolo Nogwaza, a member of the Ekurhuleni Pride Organising Committee, a gay rights group, was allegedly raped by eight men and murdered in KwaThema township near Johannesburg. Human Rights Watch said evidence suggested Nogwaza was targeted because she was lesbian. It described the murder as the latest in an epidemic of brutal homophobic attacks in South Africa and called on the government to take action.

Nogwaza's body was found in the same township where Eudy Simelane, a former South African international women's footballer, was gang raped, beaten and stabbed 25 times in the face, chest and legs.

Other alleged victims of corrective rape include Nokuthula Radebe, 20, whose body was found in Soweto in March this year, and Sizakele Sigasa and Salome Masooa, partners who were raped and murdered in 2007. A court case involving the murder of 19-year-old Zoliswa Nkonyana in 2006 has been postponed more than 30 times in five years.

Last week, the government set up a team to address hate crimes against lesbian and gay South Africans after 170,000 people around the world signed an online petition demanding action against corrective rape – a record for a campaign on the social change website change.org.

In 2006 South Africa became the fifth country in the world, and the first in Africa, to legalise gay marriage. It is a signatory to the international Convention on the Elimination of all Forms of Discrimination Against Women.

But the gap between constitutional theory and practice on the ground remains stark. Research by the country's Medical Research Council has found that one in four men admit committing rape, and one in three in Gauteng province, where Nogwaza and Simelane were attacked.

Dean Peacock, co-founder and co-director of the Sonke Gender Justice Network, said its research had found some men described feeling threatened by gender transformation, including the assertion of women's and children's rights.

He said: "When you compare South Africa with other countries, what distinguishes it is gang rape: a performance of masculinity, young men proving themselves to each other and saying to a woman: 'We're not prepared for you to assert that kind of autonomy, especially sexual autonomy'."

Peacock said that some men in post-apartheid South Africa occupied a "dangerous nexus" of patriarchy, masculinity, poverty, radical disappointment with the government, profound feelings of insignificance, and a sense they can act with impunity. But they were still individual agents able to make choices, and nothing could excuse horrendous violence against women, he said.