'We are not going to hurt you." This was the promise made by the gunmen who carjacked Shrien and Anni Dewani on Saturday night in a township near Cape Town, South Africa. They were lying. Shrien was unharmed, but Anni's body was found in the car a few hours later. The 28-year-old had been shot several times and died from a bullet wound in the neck. Two suspects have been arrested.

The Dewanis, who lived near Bristol and who were on honeymoon in Cape Town, made headlines in Britain, helped by the fact that Anni was young and beautiful. Yet their fatal decision was to explore Gugulethu, one of South Africa's impoverished townships. It has been reported that the Dewanis' hotel advised them not to go there at night. But there are many women who have no choice. They live there.

While the murder of tourists is rare, and generates international headlines, the murder of residents is not. More than 700 people have been killed in Gugulethu in the last five years, according to the South African Institute of Race Relations. On average that is one homicide every two-and-a-half days in a population of roughly 300,000.A country of 49 milion people, South Africa every year reports around 18,000 murders and 50,000 rapes. In England and Wales, with 53 million people, there are around 600 murders and 12,000 rapes a year.

Women and girls in Gugulethu, and in townships and rural areas across South Africa, are frequently the target of murder, rape and sexual violence. There is no evidence that Anni Dewani was sexually assaulted, yet a woman in South Africa is more likely to be raped than to learn to read, according to research from the One In Nine campaign. The police reported 68,332 sexual offences last year – an average of one every eight minutes – and one in four men surveyed by the Medical Research Council admitted committing rape. However, many of these crimes go unreported, with many victims remaining invisible, ignored not only by the media but by communities, police and courts.

Among those to have survived to tell the tale is a 28-year-old from Tembisa, a township near Johannesburg, who does not wish to be named. She told the Guardian how in 2006 she was working as a personal assistant to the man, who put her up in a hotel so she could be close to work. "One day he told me to come to his room. He said he had a gun collection and if I didn't come he would shoot me.

"I went to his room and found him naked in the bathroom. He violated me and raped me. It was terrible the things he made me do."

She reported the crime and the man was charged, but after a court case that dragged on for four years, he walked free. "They said it was his word against mine and there were no witnesses. They asked why didn't I scream, but what was the point of screaming?"

During the football World Cup this summer, South Africa worked hard to present a safer, friendlier face to the world and serious incidents were kept to a minimum. But violent crime rates remain high in townships and rural areas where unemployment and alcoholism run deep and life is often cheap. One of the few murder victims to gain national media attention was Eudy Simelane, a lesbian footballer.

The country has witnessed a spike in high-profile cases in recent months. A female paramedic was raped by three men in Roodepoort while attending to a toddler who had suffered burn wounds. A 35-year-old doctor was hit on the head with a brick, overpowered and raped while on night shift at Pelonomi Hospital in Bloemfontein. Twelve women in central Johannesburg were allegedly lured to a hotel room and raped by a man due to appear in court next week.

Age is no barrier to the crime: a seven-year-old girl was repeatedly raped in school toilets by three boys aged nine, 11 and 11. An 11-year-old girl was allegedly raped several times by a 48-year-old caretaker at her primary school. A statutory rape incident involving a 15-year-old girl and two boys, filmed and distributed by classmates on mobile phones, has provoked renewed soul searching.

"When will it end?" asked Phumla Matjila, a columnist in the Times of South Africa. "How can it end when our children hear adults say: 'Some women enjoy being raped' or 'They asked for it'? Why do we shudder when they repeat the words they have heard us say?"

The Sonke Gender Justice Network, a campaign group, attempts to tackle the crisis at root by working with men and boys. Bafana Khumalo, its international programmes manager, says: "We certainly have a major problem in South Africa. There is a culture permissive of sexual violence. In a society where people can get away with it with impunity, they are encouraged to feel there is nothing wrong with it.

"Apartheid was predicated on violence – the army, the security establishment, the state apparatus used it to dominate for decades. That became a culture in our society. Violence was seen as a normal part of life."

The criminal justice system is seen by many as ill-equipped to meet women's needs. Khumalo says: "Sometimes a raped woman who goes to the police is not believed . . . Sometimes they are raped by the police."

Khumalo rejects the notion that patriarchal African subcultures make sexual violence inevitable. "I find that sometimes people seek an easy escape into tribal 'tradition'. When you interrogate it further you find a certain practice was never done anywhere but it's being used to justify something now."

South Africa has been branded the "rape capital of the world" but this is perhaps unfair – its ability to measure the problem is far more sophisticated than wartorn countries such as the Democratic Republic of Congo. On the other hand, a 2002 survey found that only one in nine South African rape survivors report the attack to the police.

Yet there is a paradox in South Africa's gender crisis. In its post-apartheid constitution, "non-sexism" is given equal status to "non-racialism". The government has outlawed sexual harassment at work and given women equal rights in marriage. Women hold 44% of parliamentary seats, the third highest percentage in the world.

But the country's leaders have been accused of failing to practise what they preach. President Jacob Zuma, a traditional Zulu, has three wives and at least 21 children. He was cleared of rape in a trial, where he admitted sleeping with a family friend he knew to be HIV-positive. The Zulu king Goodwill Zwelithini, who has five wives, hosts an annual reed dance in which 25,000 bare-breasted women perform, after undergoing virginity tests.

Dumisani Rebombo was 15 when he raped a girl at his school in 1976. Twenty years later he met the victim to apologise. He is now a gender activist and senior manager at the community organisation the Olive Leaf Foundation.

"We live in a society that has known so much violence for so much time that it becomes normalised," he says. "People don't shudder and jump when they hear these things. There is a negative perception that if you don't treat women as second-class citizens, they will take over the leadership."

He adds: "We need a bigger movement. There are men who don't rape but when they see these atrocities around them they remain silent. When they speak out, we will win the battle."