JOHANNESBURG, South Africa (CNN) -- South Africa's police chief said Monday that violence directed at foreign nationals had killed 22 people over the past week.
Police carry an unidentified Malawi national on an improvised stretcher after he was badly beaten in Reiger Park township.
The attacks have been concentrated in Johannesburg's poorest areas, and many of the victims were Zimbabweans who have fled repression and dire economic circumstances.
The Nelson Mandela Foundation issued a statement condemning the "senseless violence" that police say was sparked a week ago in Johannesburg's Alexandra Township.
"We join the rest of South Africa in deploring this violence," said Achmat Dangor, CEO of the Nelson Mandela Foundation, according to a statement released on Monday.
"Whatever the underlying causes they have to be addressed, but this senseless violence is not a solution."
Police said those behind the attacks accused the foreigners of stealing jobs, carrying out criminal activities and benefiting from social services -- such as free housing -- meant to benefit South Africans. iReport.com: Are you there? Send photos, video
Police arrested more than 200 people during the violence for offenses including rape, murder, robbery and theft.
Police said at least one foreigner was burned alive over the weekend, while others had their houses torched, their shops looted and their possessions stolen. Many have sought refuge at police stations.
Some women have told police they were raped as part of an effort to drive the immigrants out.
South Africa's police director Govindsamy Mariemuthoo said 22 people had been killed in the past week. The Red Cross estimates some 3,000 more were displaced.
The attacks were concentrated in some of the poorest parts of South Africa where locals are jobless, hungry and in need of basic services such as clean water, sanitation and housing.
South African President Thabo Mbeki called for an investigation into the violence. He has been reluctant to describe it as xenophobic because many South Africans have criticized his government for not doing enough to deal with the crisis in neighboring Zimbabwe.
Zimbabwe is in the midst of an economic collapse, with nearly 80 percent unemployment and inflation estimated to be at 160,000 percent.
In addition, it is also in a state of political limbo. A presidential runoff between long-time leader President Robert Mugabe and his opposition challenger Morgan Tsvangirai is scheduled for June 27 -- three months after the initial vote.
Opposition leaders have accused the government of carrying out a campaign of political intimidation ahead of the runoff.
The economic and political situation has seen an influx of Zimbabweans to South Africa, seeking a better life.
Archbishop Desmond Tutu also condemned the violence and urged South Africans to remember the help that he and other anti-apartheid leaders received from neighboring countries.
"Although they were poor, they welcomed us South Africans as refugees, and allowed our liberation movements to have bases in their territory even if it meant those countries were going to be attacked by the SADF (South African Defense Forces)," Tutu said.
"Please stop the violence now. This is not how we behave. These are our sisters and brothers. Please, please stop."
A South African military veterans' group plans to mobilize soldiers who fought against the country's former system of legalized racial separation "to help educate the people ... about the role played by other African countries in securing South Africa's freedom."
"Many brave comrades paid the ultimate price on African soil, but never at the hands of the people of those countries," according to a statement from the Military Veterans' Association in the Western Cape province.
"In the light of these facts, the xenophobic attacks witnessed in Gauteng (Province) over the past week -- and previously, against refugee traders in Cape Town -- are totally repugnant."