More than 80 people were killed between October 2025 and July this year following false accusations about what is termed "genital theft", the BBC Global Disinformation Unit has found after gathering data from police forces across six African countries.
The killings are linked to rumours that a simple tap on the shoulder can cause a man's genitals to shrink or disappear. They are being fuelled by widespread misinformation on social media.
"They were shouting that we had stolen someone's genitals and we didn't have any way to escape because there was a huge crowd," Tanzanian mechanic Boniface Mgala told the BBC about his ordeal in April when he was badly beaten by those convinced he was a genital thief.
His experience was similar to those in videos seen by the BBC: men claim that their genital organs - penis and testicles - have vanished or shrivelled after coming into contact with strangers and a mob then demands that alleged perpetrators return what they have supposedly stolen.
Such claims are rooted in longstanding fears and superstitions - and are not new on the continent, particularly in communities where belief in witchcraft remains widespread. Social media has amplified these fears.
The recent wave of rumours appears to have started last year in the Democratic Republic of Congo, where similar claims had surfaced in 2008.
They progressively spread across the region to Burundi, Zambia and Tanzania as well as Mozambique, Angola, Malawi and Kenya.
In Zambia, the hearsay about disappearing genitals first gained traction in March when a woman was lynched, going on to spread panic across the border in Tanzania.
At his home in Mpemba near Tunduma, a busy trading town in Tanzania by the border with Zambia, Mgala traces his fingers along the sickle-shaped scar that runs down the right side of his head as he reflects on his traumatic experience.
"If I had known how close I would have come to death on that day, I wouldn't have gone into that restaurant to eat. Only we don't know how close death is," the mechanic says.
He and his friend had gone into Tunduma on 1 April to meet a client about a car sale and decided to eat lunch beforehand. They had not long sat down in the restaurant when they were dragged outside by a mob.
Two smaller scars on his chin and a missing tooth are other visible marks of his ordeal.
Amid the beating, he lost consciousness. Mgala regained awareness in hospital two days later to news that his friend had been killed.
Back at his house where he lives with his wife and their four children, he now walks with a limp and says he also suffers from constant headaches.
He has not been able to return to work at his mechanic shop but says neighbours and friends have helped cover the cost of some of the medicine he needs.
On the same day that Mgala and his friend were attacked, commercial photographer and businessman Michael Silavwe says he witnessed another similar assault in Tunduma, where he says anxiety had been building after videos about stolen genitalia had begun circulating on TikTok.
Outside his shop he saw people running and says he learned that a man had been accused nearby and was being beaten - and later set on fire.
"After they set him on fire, the police arrived at the scene and everyone scattered and ran away," the 23-year-old told the BBC.
In a video of the attack verified by the BBC Global Disinformation Unit and viewed more than 100,000 times across TikTok and Facebook, a group is seen beating a man while demanding he return the victim's allegedly stolen genitals.
"Those incidents kept escalating and people kept getting beaten," Silavwe said, adding that at the time young people like him did feel scared, but he understands now there is no truth to the rumours.
Asha Steven Mwakilasa, a 50-year-old tailor and fashion designer in Tunduma, which is in Momba district, agrees: "I came to realise it was not true."
This does not stop her anxiety - especially if her husband or sons are out, but she says she is grateful that the police are now mounting patrols.
Momba district commissioner Elias Daniel Mwandobo told the BBC local investigations suggested there was deliberate criminal intent behind some of the incidents: "Individuals conspired to commit a crime and incite public panic for their own benefits."
Another video recorded in Tanzania's main city of Dar es Salaam shows a crowd marching a man down a dusty market street, pushing, grabbing and striking him and insisting he returns the genitalia, as the man pleads his innocence.
The BBC Disinformation Unit verified similar videos of attacks in Mozambique and Kenya.
Dozens of these recordings of mob violence, alleged first-person accounts, warnings about alleged incidents, commentary and videos framed as reports of events in particular areas are circulating across TikTok and Facebook.
Many of those analysed by the BBC, including some showing mob violence, remain online.
"We are reviewing the content shared with us and will take action on those that are found to violate our policies," a Meta spokesperson told the BBC.
TikTok has yet to respond to a BBC request for comment.
With some social media creators, who warn viewers to be vigilant, it is often unclear whether they believe the claims or are primarily seeking engagement.
Alongside these posts, some users promote so-called charms said to protect against genital theft, while comedians have parodied the claims through comedy skits.
Smartphones and social media make rumours spread faster, reach larger audiences and become more difficult to control once they begin circulating, says author Julien Bonhomme.
His book, The Sex Thieves: The Anthropology of a Rumor, examines how hearsay about "sex thieves" spread and why people believe them.
People are not simply hearing claims that someone has lost his genitals - they are seeing distressed men say it has happened to them, or watching crowds respond to accusations, he says.
Videos shared on social media can make unverified claims appear more believable, he says, because of their immediacy, describing this as "one of the most significant differences" between the current digital environment and earlier outbreaks.
The worst-hit country has been Mozambique, where the police said in May that 55 people had been killed in six weeks, including a police officer, health workers and civil servants.
Mozambique's President Daniel Chapo publicly condemned widespread rumours and deaths, saying the claims were false and the government had found no medical evidence to suggest anyone had lost a part of their body.
The two healthcare workers were attacked at their home and workplace in April in Cabo Delgado province - a region that borders Tanzania which has been affected by an Islamist insurgency for nearly a decade.
The health facilities in the areas of the attacks had to close for weeks while the authorities launched public awareness campaigns to counter the claims.
As part of the health campaign, the government said some of the fears could be linked to Koro syndrome, a mental illness otherwise known as missing or genital retraction hysteria.
The most recent incidents of violence have occurred in Kenya, where five people were killed by mobs in the coastal counties of Kwale and Mombasa.
After the first incidents were reported in July, Mombasa County Commissioner Mohamed Noor blamed some content creators for spreading the claims to boost engagement "simply to attract views and attention".
"Such misinformation can easily lead to loss of life," Noor told the BBC.
He said police had since contained the violence and made several arrests, including a father and son who were sentenced to a year in prison after pleading guilty to assaulting a woman they accused of causing men's genitals to disappear.
Similar claims also fuelled mob attacks in Malawi, leaving eight people dead.
Back in Tunduma, in neighbouring Tanzania, even as mechanic Mgala recovers from the physical impact of the assault, the emotional pain is still raw.
"It still hurts me deeply when I think back to the senseless manner my friend died because I still don't know what was going on," he said.
"To suddenly find yourself being pelted with stones for no reason, and then end up losing your life?"
