On Thursday, the South African minister of international relations, Lindiwe Sisulu, described the tweet as “regrettable” and “based on false information.” The government said it would seek clarification from the United States Embassy, and Ms. Sisulu planned to “communicate with Secretary of State Michael Pompeo on the matter through diplomatic channels.”

The government has said expropriating farms is necessary to deal with longstanding inequities and that only unused land would be subject to seizure, suggesting that land that is being actively farmed would be safe.

In a country still struggling with the effects of apartheid and widespread economic inequality decades after Nelson Mandela became the country’s first black president, Mr. Trump’s tweet was likely to inflame the divisive landownership debate.

Are there widespread killings of farmers?

The number of killings of farmers, including farm workers, is at a 20-year low, 47 in the fiscal year 2017-18, according to research published in July by AgriSA, a farmers’ organization in South Africa. That is down from 66 during the fiscal year before. The figures were consistent with a steady decline of violence since a peak in 1998, when 153 were killed.

South Africa recorded 19,016 murder cases from April 2016 to March 2017, according to the South Africa Police Service. The national murder rate last year was 34.1 per 100,000 people, but the number of people living on farms is not fully known, which makes comparisons difficult.