(BSS/AFP) - South Africa faces nationwide anti-immigrant marches after hardline citizen-led groups ordered undocumented foreigners to leave the country by Tuesday.

The unrest has already killed at least four people, with thousands of African migrants fleeing home or huddling in makeshift camps for fear of attack.

Here are four things to know about the protests.

Who is behind them? -

Protests have been mobilised by a loose coalition of minor political parties and small citizen-led vigilante groups, some fronted by men in traditional Zulu attire and carrying sticks and shields.

They claim migrants drive crime and take jobs from locals, fuelling tensions in townships grappling with poverty, unemployment and weak policing.

The groups seem well organised and well resourced, analysts say, and have a strong presence on social media that includes disinformation debunked by AFP.

"The main ingredient is right-wing political opportunism," political scientist Sandile Swana told AFP.

"We are seeing a new form of black-on-black violence diverting attention from the true culprits of the economic crisis."

Why now? -

Mostly low-key demonstrations flared late last year when undocumented foreign nationals were blocked from accessing clinics and hospitals.

Protests intensified this year with vigilante groups warning irregular migrants to go home by June 30.

They were driven by growing public anger in Africa`s richest nation over issues such as soaring joblessness -- at nearly 33 percent -- crime and pressure on resources, analysts say.

They say a steady influx of mostly African migrants have become a convenient scapegoat, with political actors leveraging the tensions ahead of municipal elections in November.

There are roughly three million immigrants in the country, about 5.1 percent of the population, according to the national statistics agency.

More than 63 percent come from other countries in southern Africa, many of which are facing economic crisis and political instability.

What has happened? -

South African police are investigating the killings of two Mozambique nationals and a Malawian in the recent unrest.

There have also been reports of South Africans demanding to check the papers of foreign nationals, or going to their homes or workplaces to tell them to leave.

Some of those heading home say they were told to go by their employers or landlords who feared being fined by inspectors or attacked by vigilantes.

The violence, threats and intimidation have prompted several African countries -- including Kenya, Uganda and the Democratic Republic of Congo -- to organise voluntary repatriations.

At least 988 Ghanaians and about 600 Nigerians left by plane this month, the Border Management Authority (BMA) said.

More than 15,000 people crossed land borders into Zimbabwe, Malawi and Mozambique over the same period, it added.

The BMA told AFP on Monday that some 25,000 people had been repatriated in recent weeks.

The agency said most people it had processed were in the country illegally, some of them having overstayed their visas.

Thousands more foreign nationals were meanwhile in makeshift camps in the eastern city of Durban, or centres in Johannesburg and Cape Town, awaiting assistance to return home.

Ahead of Tuesday`s unofficial deadline, government officials outlined their actions against illegal immigration -- including reinforcing border controls and inspections -- and called for calm.

How this compares to past protests -

Waves of xenophobic violence have swept South Africa over the past decades.

In 2008, 62 people were killed in anti-immigrant riots and thousands were displaced. Further outbreaks followed in 2015 and 2016.

Violence in 2019 saw armed mobs descend on foreign-owned businesses around Johannesburg, leaving at least 12 people dead -- 10 of them South African citizens.

But this is the first time that such threats have prompted several governments to simultaneously organise coordinated voluntary repatriations for thousands of their nationals.