South Africa needs to do more to protect lesbians who have become targets for murder, US-based Human Rights Watch (HRW) has said.
Black lesbians often endure the worst abuse for being gay
Three lesbians were brutally killed in July and non-governmental organisations suspect the victims were raped too.
HRW said a "climate of violent homophobia" existed in South Africa.
"Despite legal commitments to equality for all, lesbians in South Africa are still targeted for rape and murder," says HRW's Jessica Stern.
South Africa's constitution is one of the most advanced and progressive anywhere in the world.
In an effort to reverse the wrongs of apartheid, it ensures that human rights, gender equality and gay and lesbian rights are all properly protected.
Last year, same-sex weddings were legalised in South Africa - the first country to do so in Africa, where homosexuality is often seen as taboo.
HRW's comments were made in a letter to South Africa's President Thabo Mbeki as the country celebrated National Women's Day.
It asked the government to take action to "make its commitment to equality and tolerance a reality for the nation's gays and lesbians".
HRW detailed the cases of recent lesbian killings.
Last month, two lesbians in Soweto were attacked and shot dead, their bodies were found in a field.
Later in the month, the body of a naked lesbian in Ladysmith in KwaZulu-Natal was discovered in a field with multiple head wounds.
According to HRW, the police have refused to speculate on whether the victims' sexual orientation was a motive for their murders.
In an earlier case in March, a lesbian in a township near Cape Town was attacked and killed by a mob.
HRW says a friend walking with the woman said their attackers called them "tomboys" who "wanted to be raped".
Correspondents say despite laws that are favourable towards lesbians and gay men, discrimination remains common and black lesbians endure the worst abuse.