They turned up in a mob of several hundred at a migrant centre in South Africa's Soweto township – unemployed, wielding weapons and angry with foreigners they accuse of taking their jobs.
"Foreigners, go home," they cried, according to witnesses.
With unemployment at 35 per cent – and rising up to 65 per cent among youth – competition for jobs has spawned resentment among some jobless South Africans.
In the past, xenophobic protests have morphed into violence. Attacks against foreigners left at least 62 people dead in 2008, while another seven were killed in similar unrest in 2015.
Armed mobs descended on foreign-owned businesses around the financial hub Johannesburg in 2019. The ensuing clashes left at least 12 people dead, of whom 10 were South African, according to the government.
In recent weeks, scores of protesters have been staging demonstrations against undocumented migrants in what they have dubbed Operation Dudula, Zulu for "drive back".
At the Methodist migrant community centre in Soweto, where about 100 migrant families live, there had been rumours of an attack.
A horde arrived earlier this month – some wielding traditional Zulu leather whips – at the centre in South Africa's most famous township, located south of Johannesburg.
"Foreign nationals are stealing jobs that belong to South Africans," protesters said, according to witnesses.
Sithulisiwe Chinora, a 22-year-old Zimbabwean, recounted how she started shaking violently, her infant wrapped on her back.
"I thought I was going to die that day," she said.
Father Paul Verryn, who founded the centre, says it is clear who the protesters were.
"They are xenophobic activists, they clearly targeted foreign nationals because they want them out," said the minister, who is famous for having opened a church in Johannesburg to thousands of undocumented Zimbabweans after the first anti-immigration attacks.
But the Operation Dudula movement says it is pacifist.
Its leader Nhlanhla Lux Dlamini, a man in his thirties from Soweto who often dresses in a military uniform and bullet-proof vest, says he is simply seeking to "restore law and order".
"The law enforcement is failing us," he has told reporters.
On February 19, Dlamini was among some 2,000 people protesting in Johannesburg's inner-city suburb of Hillbrow.
Among the crowd, Bhekani Thusi, 38, was one of those who said they were "tired of foreigners".
"We are here to claim our land back. Our space is occupied by foreigners," he said.
The previous weekend, the same movement held a protest outside a supermarket demanding the sacking of foreign workers employed there.
"There is [nothing] xenophobic about that, it's the law," he told journalists. "Any job that doesn't require skill in South Africa belongs to South Africans."
Around 3.9 million foreigners live in South Africa, a country of almost 60 million, including political refugees, according to official statistics.
So far, the latest demonstrations have not spiralled into violence.