Three men have been found guilty by a court in Tanzania for murdering an albino boy, in a ruling that campaigners hope will help protect the minority group from being slaughtered for their body parts. The landmark verdict is the first time anyone has been convicted of killing an albino despite more than 50 murders in the past three years.

Albinos – who suffer from a genetic defect that alters their skin and hair pigmentation – have been targeted by modern day witch doctors in East Africa who believe their body parts add potency to black magic rituals.

A string of brutal attacks in which members of the minority group have been literally hacked to pieces, with children as young as five being killed, has provoked angry criticism of the government. Tanzania, while an extremely poor country, has long enjoyed relative stability and is renowned for its spectacular national parks and Indian Ocean coastline.

Download the new Independent Premium app Sharing the full story, not just the headlines

The President Jakaya Kikwete has spoken out against the killers and banned witch doctors earlier this year, while police have arrested scores of suspects but Tanzania's justice system is notoriously slow and yesterday's conviction was the first of its kind.

The court in the north-western Shinyanga district, close to the shore of Lake Victoria, sentenced the three men to death by hanging for the murder in December last year of 14-year- old Matatizo Dunia. One of the accused was found with both of the boy's legs when he was arrested.

There are an estimated 17,000 albinos in Tanzania and some researchers believe the genetic defect may have originated in East Africa. Today many albinos in the region suffer intense prejudice and are routinely referred to as "zerus" or invisibles.

The skin, hair, eyes and limbs of albinos can command thousands of dollars on the black magic market in Tanzania. These sums – often paid by educated, ambitious city dwellers who travel to rural witch doctors for help with business, family or sexual problems – have been sufficient for freelance killers to hunt the pale-skinned minority.

At least 53 murders have been recorded since September 2007 with the most recent killing taking place last month. While most of the attacks have taken place in the Shinyanga and Mwanza areas in the north-west, albinos are at risk all over the country and body parts have turned up in neighbouring Burundi, the Democratic Republic of Congo and Kenya.

The Tanzanian Albino Society (TAS) had been warning for years of the growing threat to their community but found initially that there was little official interest in the killings. The UK-based agency, Action on Disability and Development (ADD), which supports TAS, said it "applauds the efforts of the Tanzanian authorities to bring the perpetrators to justice" but called on the courts to commute the death sentences to life imprisonment on appeal.

Since last year, authorities in Tanzania, stung by an international outcry, have launched a public awareness campaign to attack the superstitious beliefs and last year the President appointed the country's first albino MP, the 48-year-old Al-Shymaa Kway-Geer.

There have been 90 arrests so far in the huge East African nation, including four police officers, which has confirmed fears in some quarters that there is official involvement in some of the killings. There are another 15 cases going through the courts in the country.

A local BBC journalist, Vicky Ntetema, was last year forced to flee Tanzania after receiving a string of death threats following an undercover investigation into the trade in body parts.

A Canadian businessman and campaigner, Peter Ash, himself albino, said authorities must pursue the killers in every case. "This is one conviction. There are 52 other families still awaiting justice," he said.

Speaking before the trial on a tour of the country, the campaigner who set up the Under the Same Sun organisation, highlighted the case of a five-year- old girl named Mariam. She was attacked by a group of men in the city of Mwanza. "One of them slit her throat, drained her blood into a saucepan and drank it in the presence of her two siblings," he said. The men then chopped off her limbs and ran off. "Mariam did not have the benefit of being unconscious first," he added. "She was killed, like an animal, by grown men who did this deliberately while her siblings watched."