SOWETO, South Africa—Sello Kgoale watched his neighbors shuttling back and forth with looted liquor, refrigerators and flat-screen televisions. There were no police at a nearby mall, they told him, so the 46-year-old father of three joined the thousands-strong mob ransacking the shopping center and filled three bags with rice, cooking oil and paraffin for his family’s cooking stove.

“I’ve never done anything like this before. I’m ashamed,” he said last week, sitting in his corrugated-iron shack. “But we just keep getting hit.”

Sixteen months ago, Mr. Kgoale lived in a rented two-bedroom house and had a steady cleaning job, while his wife worked in a call center. South Africa’s first wave of Covid-19 infections took the lives of his mother-in-law and grandmother. The second cost him his job and then his home. The third destroyed his efforts to start a new business. “I came to Johannesburg 21 years ago from the north, full of hope,” he said. “Now we have nothing left but anger.”

Wave after wave of coronavirus is pummeling South Africa’s fragile economy and its largely unvaccinated population, creating a spiral of death, lockdowns and anger that has fueled the country’s worst rioting since the collapse of white minority rule in 1994. At least 215 people died in the violence across South Africa’s two most populous provinces, and more than 3,400 have been arrested. While the looting had quieted by Monday, the situation remains tense in parts of the country.

Saaberie Chishty paramedic Farah Williams said that after weeks of back-to-back calls from patients, the phones went quiet last week during the riots.

Saaberie Chishty paramedic Farah Williams said that after weeks of back-to-back calls from patients, the phones went quiet last week during the riots.

The violence was initially sparked by the arrest of former President Jacob Zuma earlier this month, and has exacerbated a power struggle within the African National Congress, South Africa’s ruling party since Nelson Mandela’s election as the country’s first Black president 27 years ago. President Cyril Ramaphosa has said the unrest was an attempted insurrection against South Africa’s democracy and intended to sabotage its economy.

The political protest quickly devolved, becoming an outlet for the frustrations of an impoverished majority long shut out of the country’s economy. South Africa is struggling to emerge from a record contraction of 7% last year. Each surge of Covid-19 and the subsequent lockdowns are putting more pressure on the divided nation, where 43% of workers were without a job at the end of March.

“We were sitting on a dormant volcano here, where all of us might perish if it erupts,” said Xolani Dube, a political analyst with the Xubera Institute for Research and Development, a nonpartisan think tank in the southeastern city of Durban. “Now the volcano has erupted.”

The human and economic dislocation in South Africa, where just 2.8% of people have been fully vaccinated against Covid-19, shows how difficult it will be for many emerging economies to recover from the pandemic. The violence in South Africa—as well as in countries including Colombia and Sudan—offers a stark example of how diminishing incomes and the rising cost of food are adding to more than a year of pandemic suffering, exacerbating political instability.

The World Bank estimates that more than 160 million people will have been pushed into poverty as a result of Covid by the end of 2021, widening the gap between the world’s richest and poorest nations. The pandemic has led 41 million people to the brink of famine, according to the World Food Program.

Members of the South African National Defence Force during a raid for looted goods in Johannesburg on Saturday.

Members of the South African National Defence Force during a raid for looted goods in Johannesburg on Saturday.

In South Africa, Mr. Ramaphosa called in army reservists to restore law and order, while the country’s overcrowded hospitals and first responders fought the country’s third, and highest, surge in Covid-19 infections.

When the pandemic arrived, South Africa was already, by some measurements, the most inequitable country on earth. Nearly two-thirds of Black South Africans, who make up around 80% of the country’s population, lived in poverty, according to the national statistics office. The mean monthly income of white South Africans was more than three times that of their Black compatriots.

Mr. Ramaphosa, elected on a pledge to clean up the country’s corruption-riddled politics and revive a moribund economy, imposed one of the world’s strictest lockdowns in response to Covid-19.

In the economic downturn that followed, low-income earners, many of whom are Black or members of other racial groups disadvantaged under apartheid, were nearly four times as likely to lose their jobs as high-income earners, the World Bank said in a report this month. Some 13 million South Africans, including three million children, live in households that no longer have enough money to afford food, a recent, nationally representative survey found.

South Africa has lost more than 190,000 of its 60 million citizens—about one in 300—to the coronavirus since May 2020, according to a tally of excess deaths by the government-funded South African Medical Research Council. A nationwide study of donated blood determined that by May this year, 47% of South Africans have already had Covid-19, with Black donors more than three times as likely to have antibodies to the virus than white donors.

As the third virus wave arrived, powered by the more transmissible Delta variant, South Africa’s Constitutional Court on June 29 made what appeared to be a decisive ruling in a long-running battle within the ruling party: convicting Mr. Zuma.

Recent graves at the Avalon Cemetery in Johannesburg.

Recent graves at the Avalon Cemetery in Johannesburg.

The former president had resigned in 2018 under pressure from Mr. Ramaphosa. The court sentenced the 79-year-old Mr. Zuma to 15 months in jail for contempt of court after he refused to testify at a government commission investigating allegations of rampant government corruption. Mr. Zuma, a former ANC spy chief who spent 10 years in the notorious Robben Island prison during the antiapartheid struggle, has denied wrongdoing.

Africa’s oldest liberation movement, the ANC has been roiled for decades by ideological struggles that have become more complicated by mounting corruption allegations. In one faction are supporters of Mr. Ramaphosa, a union-leader-turned-millionaire-businessman who sees South Africa as a largely market-driven economy in which foreign investment can bring prosperity for all races. The opposing side is embodied by Mr. Zuma, who has denounced “white monopoly capital” and called for “radical economic transformation” of an economy that has failed to provide for many Black South Africans.

Within days of Mr. Zuma’s arrest, his supporters were disseminating plans for a violent protest through messaging apps and social media. His charitable foundation and his daughter Duduzile claimed on Twitter that the former president had been arrested without trial and urged supporters to fight for his release.

In one WhatsApp group, whose messages were reviewed by The Wall Street Journal, leaders of local ANC constituencies in Mr. Zuma’s home province of KwaZulu-Natal were asked to mobilize at key locations around the city of Durban.

Mr. Ramaphosa said Friday that some rioters targeted critical infrastructure, including telecommunications towers, oil refineries, the largest maker of HIV/AIDS drugs and the Durban port—the largest in sub-Saharan Africa—suggesting a coordinated operation to dislodge South Africa’s constitutional order. The highway between Durban and Johannesburg, a key route for imports, exports and domestic trade, was blocked for five days. Fears of shortages of food and other essentials prompted panic buying.

Government officials said Monday that six alleged unnamed instigators have been arrested and charged with inciting public violence, and that more arrests were expected.

“The JZ incident was just a spark for what had been brewing over the years,” said Bob Mhlanga, a former intelligence officer under Mr. Zuma who is now in private security, using the former president’s initials. “We will face another revolt if we don’t address socioeconomic issues.”

Members of the South African National Defence Force walked away after a raid for looted goods on Saturday.

Members of the South African National Defence Force walked away after a raid for looted goods on Saturday.

The unrest was yet another threat to reckon with for the nation’s first responders in South Africa’s coronavirus emergency. The team at Saaberie Chishty, an ambulance service run by a Muslim charity in southern Johannesburg, had already been running triage in patients’ homes. Hospital beds often only opened up when someone died.

“This third wave is the worst,” said Farah Williams, a paramedic who had six of her close colleagues die from the virus within a span of three months. After weeks of back-to-back calls from patients, the phones suddenly went quiet last week. “Everybody is fearful…to seek attention or care,” she said. When she did venture out, it was often to declare another death amid mounting fears for her own safety.

In the riots, two ambulances in the province were torched, another robbed of its equipment. One Saaberie Chishty volunteer who had joined a group defending his community saw a neighbor get shot in the head. “We couldn’t get an ambulance to him,” Ms. Williams said.

The violence disrupted Covid-19 testing and a vaccination drive that was finally gaining momentum. Government officials and scientists warn that the mass lootings and other gatherings are likely to power another rise in infections, hospitalizations and deaths.

Farah Williams texted colleagues while on a call to do a declaration of death.

Farah Williams texted colleagues while on a call to do a declaration of death.

Mr. Kgoale had been looking for odd jobs until last week Monday, when he saw residents returning to the squatter camp carrying looted items.

His family had moved there after he was laid off, renting a one-roomed shack made of corrugated iron with a plastic mat laid on the dirt floor. Anger against politicians and lack of economic opportunities seethed in the community, which refused to allow government officials onto the settlement.

“No heating and no water. We’ve never lived somewhere like this,” he said. His oldest son had been due to go to college in January, but the family could no longer afford it.

Using his severance money, Mr. Kgoale started a chicken-breeding business that would deliver birds reared in his home state of Limpopo to stores and food stalls he had already identified in Johannesburg. A June lockdown that banned movement between provinces killed that revenue stream, too.

After arriving in Johannesburg in the early days of democracy, Mr. Kgoale plans to move back to Limpopo, a largely rural community with one of the country’s highest unemployment rates. “There’s nothing for me there,” he said. “I can only hope for my children, but I worry it’s too late.”

A squatter camp close to the recently looted Bara Mall in Soweto.

A squatter camp close to the recently looted Bara Mall in Soweto.

—Gulshan Khan contributed to this article.

Write to Gabriele Steinhauser at gabriele.steinhauser@wsj.com and Joe Parkinson at joe.parkinson@wsj.com