Ngeme Luhagula has not had a peaceful night’s sleep since she saw her daughter hacked to death before her eyes two years ago.

“I have endured the torture of living with that pain ever since. The images come and haunt me every night,” she told The Times at her village home on the shores of Lake Victoria.

Yesterday she could not suppress a smile when informed that four men had been sentenced to hang for killing a 50-year-old man — an albino who had the same condition as her 18-year-old daughter, Vumilia.

The men were found guilty of murdering Lyaku Willy and cutting off his head and legs. The verdicts bring to seven the number of people sentenced for killing albinos after the first such convictions in September.

“I want these killers to be hanged in public so that the punishment would act as a lesson and deter other killings,” Ms Luhagula said quietly. Over the past three years a wave of killings of albinos has swept Tanzania, driven by witch doctors who make magic potions from the body parts of people with the condition. These concoctions sell for thousands of pounds.

Demand for the body parts comes from people looking for magical assistance, from illegal miners looking for help in their search for gold and gems, or fishermen who believe that by tying body parts in their nets they will have increased catches.

The murder of more than 50 albinos, some of them as young as 6, has spoilt the Tanzania’s image as one of the most liberal and stable countries in Africa.

The recent rulings have been widely welcomed, although critics say that criminal gangs and the main players behind the trade have not been brought to justice.

“These prosecutions will be useless if the Government does not provide security, good housing and help albino children to get access to education,” said Ms Luhagula, whose daughter sold peanuts in Mwanza. “ Prosecutions alone will not stop the killings.”

Although Tanzania still has the death penalty, no executions have been carried out since 1995.

The murders have spread to neighbouring Congo and Burundi, where at least 12 albinos have been butchered and their body parts smuggled over the border.

All over Tanzania albinos live in fear. Until recently Joyce Makunda’s proudest possession was her school uniform. The 15-year-old dressed meticulously each day. After escaping a murder attempt just over a year ago she now rarely leaves her home.

"Two men I had not seen before started following me and then called me towards them. They got angry and shouted that no matter how fast I ran they would get me some time,” she said.

Born with a genetic defect that affects skin pigmentation, albinos suffer abnormally high rates of skin cancer and harsh light damages their ultra-sensitive eyes. Many suffer from skin cancers from the age of 10. Few live beyond 30.

“This will not come to an end now until we are all dead,” Zaida Nsembo, a 50-year-old albino woman, said. “Our bodies have become a business — they will pay as much as 5 million Tanzanian shillings (£2,500) for our right leg and arm alone. It is a secret who buys our bodies but it is here in Tanzania. I cannot call this place home now.”

Genetic legacy

• Albinos have little or no pigment in their eyes, skin, or hair and frequently suffer vision problems. They have inherited altered genes that do not produce the usual amounts of the pigment melanin

• In Britain one in 17,000 people is born with albinism

• It is a myth that all albinos have red eyes. Most have blue eyes

Sources: The National Organisation for Albinism and Hypopigmentation and The Albinism Fellowship

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