More than 178,000 African migrants have left South Africa in recent months, driven by a government crackdown on undocumented migration and, in some cases, violent anti-immigration protests that have fueled fears of attacks.

The departures represent one of the most significant migrant exoduses from Africa’s most industrialized economy in years.

The figures come from authorities in the migrants’ home countries. More than 115,000 Zimbabweans have returned home since late May, according to the Zimbabwean government, while Malawi says more than 56,000 of its citizens have returned.

Nigeria, Ghana, Mozambique and Lesotho have each reported the return of more than 1,000 citizens from South Africa.

The returns include people deported by South African authorities as well as migrants who voluntarily returned through repatriation programs offered by South Africa or their home countries. Voluntary returns account for the vast majority of those who have left.

South Africa said this week that about 19,000 people had been officially deported since April.

Advocacy groups have raised a series of concerns over the sudden movement of people, including the thousands of children who have been pulled out of schools and people living with HIV who have been cut off from lifesaving treatment.

The mass movement underscores the complications of migration within Africa, even as international attention is increasingly focused on migration from Africa to Europe, including a crisis sparked this month by more than 70,000 people scrambling across the border from Morocco into the Spanish territory of Ceuta.

In South Africa, groups have held a series of protests against illegal migration this year, culminating in nationwide demonstrations June 30, which the groups said was a "deadline" for migrants in the country illegally to leave.

The groups have claimed that undocumented migrants are contributing to South Africa’s high unemployment rate by taking jobs while also putting pressure on public services. For decades, South Africa, the region’s richest country, has drawn millions of migrants from other African nations to work on farms, in restaurants, in construction and in other low-paid sectors.

South Africa’s latest census data, from 2022, showed there were 2.4 million foreign nationals in a total population of 62 million, although protest groups contend that many more migrants are in the country without documentation.

The protests against illegal migration in South Africa have been accompanied by door-to-door campaigns by mobs. Rights groups say migrants have been threatened and attacked, and their homes or businesses burned, including those of some migrants who were in the country legally.

Mozambique’s government said 11 Mozambicans have been killed in attacks in South Africa, while Nigeria and Ghana also said some of their citizens were killed. South Africa has disputed the numbers, saying some of the deaths were connected to crimes such as robberies rather than migration protests. Some killings are under investigation by police.

The violence has led to unusual diplomatic tensions between South Africa and other African nations, which have accused it of xenophobia.

Ghana pushed for the issue of what it alleged were South Africa’s anti-migrant and xenophobic policies to be placed on the agenda of an African Union meeting in October. South Africa blocked the move but called for broader talks on migration in Africa.

UNICEF and the U.N. Committee on the Rights of the Child said in a joint statement that they were deeply concerned about the fate of children caught up in the returns. They face heightened risks of violence, exploitation, family separation and psychological distress, "particularly when movements are sudden, undocumented and uncoordinated," the agencies said.

While some governments have not released full figures, Malawi said nearly 4,000 children under age 5 were among those who returned from South Africa. The Zimbabwe Exemption Permit Coordinating Committee, a nongovernmental organization, estimated that more than 11,000 children had returned to Zimbabwe by mid-July. The government has instructed schools not to discriminate and to try to find places for returning children.

Health officials and aid groups say many migrants fled South Africa without medication or medical records, raising fears of interrupted HIV treatment in a region with some of the world’s highest infection rates.

Doctors Without Borders, or MSF, established clinic tents at Zimbabwe’s Beitbridge border post to treat people "who are traumatized" after losing access to lifesaving HIV medication and treatment for other chronic conditions.

South African authorities said Friday that about 3,000 people were still awaiting deportation at a migrant detention center near Johannesburg, while around 6,300 inspectors had been deployed nationally to check whether workplaces were illegally employing migrants without documents.

South African President Cyril Ramaphosa has condemned acts of violence against migrants but also acknowledged government failures in enforcing immigration laws. He has promised more technology and personnel to secure borders, new immigration courts to expedite deportations, and stricter penalties for those who employ migrants without documents.